text: #include <assert.h>
  #include <drm_fourcc.h>
  #include <GLES2/gl2.h>
  #include <GLES2/gl2ext.h>
  #include <stdint.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <unistd.h>
  #include <wayland-server-protocol.h>
  #include <wayland-util.h>
  #include <wlr/render/egl.h>
  #include <wlr/render/interface.h>
  #include <wlr/render/wlr_renderer.h>
  #include <wlr/types/wlr_matrix.h>
  #include <wlr/types/wlr_linux_dmabuf_v1.h>
  #include <wlr/util/log.h>
  #include "render/gles2.h"
  
  static const GLfloat verts[] = {
  	1, 0, // top right
  	0, 0, // top left
  	1, 1, // bottom right
  	0, 1, // bottom left
  };
  
  static const struct wlr_renderer_impl renderer_impl;
  
  struct wlr_gles2_renderer *gles2_get_renderer(
  		struct wlr_renderer *wlr_renderer) {
  	assert(wlr_renderer->impl == &renderer_impl);
  	return (struct wlr_gles2_renderer *)wlr_renderer;
  }
  
  static struct wlr_gles2_renderer *gles2_get_renderer_in_context(
  		struct wlr_renderer *wlr_renderer) {
  	struct wlr_gles2_renderer *renderer = gles2_get_renderer(wlr_renderer);
  	assert(wlr_egl_is_current(renderer->egl));
  	assert(renderer->current_buffer != NULL);
  	return renderer;
  }
  
  static void destroy_buffer(struct wlr_gles2_buffer *buffer) {
  	wl_list_remove(&buffer->link);
  	wl_list_remove(&buffer->buffer_destroy.link);
  	// EGLStreams buffers do not use FBOs
  	if (!buffer->buffer->egl_stream) {
  		struct wlr_egl_context prev_ctx;
  		wlr_egl_save_context(&prev_ctx);
  		wlr_egl_make_current(buffer->renderer->egl);
  
  		push_gles2_debug(buffer->renderer);
  
  		glDeleteFramebuffers(1, &buffer->fbo);
  		glDeleteRenderbuffers(1, &buffer->rbo);
  
  		pop_gles2_debug(buffer->renderer);
  
  		wlr_egl_destroy_image(buffer->renderer->egl, buffer->image);
  	
  		wlr_egl_restore_context(&prev_ctx);
  	}
  
  	free(buffer);
  }
  
  static struct wlr_gles2_buffer *get_buffer(struct wlr_gles2_renderer *renderer,
  		struct wlr_buffer *wlr_buffer) {
  	struct wlr_gles2_buffer *buffer;
  	wl_list_for_each(buffer, &renderer->buffers, link) {
  		if (buffer->buffer == wlr_buffer) {
  			return buffer;
  		}
  	}
  	return NULL;
  }
  
  static void handle_buffer_destroy(struct wl_listener *listener, void *data) {
  	struct wlr_gles2_buffer *buffer =
  		wl_container_of(listener, buffer, buffer_destroy);
  	destroy_buffer(buffer);
  }
  
  static struct wlr_gles2_buffer *create_buffer(struct wlr_gles2_renderer *renderer,
  		struct wlr_buffer *wlr_buffer) {
  	struct wlr_gles2_buffer *buffer = calloc(1, sizeof(*buffer));
  	if (buffer == NULL) {
  		wlr_log_errno(WLR_ERROR, "Allocation failed");
  		return NULL;
  	}
  	buffer->buffer = wlr_buffer;
  	buffer->renderer = renderer;
  	if (buffer->buffer->egl_stream) {
  		// We're rendering to a EGL surface,
  		// No need for special wrapping magic here.
  		assert(buffer->buffer->egl_stream->surface);
  		buffer->fbo = 0;
  		buffer->rbo = 0;
  	} else {
  		struct wlr_dmabuf_attributes dmabuf = {0};
  		if (!wlr_buffer_get_dmabuf(wlr_buffer, &dmabuf)) {
  			goto error_buffer;
  		}
  
  		bool external_only;
  		buffer->image = wlr_egl_create_image_from_dmabuf(renderer->egl,
  			&dmabuf, &external_only);
  		if (buffer->image == EGL_NO_IMAGE_KHR) {
  			goto error_buffer;
  		}
  
  		push_gles2_debug(renderer);
  
  		glGenRenderbuffers(1, &buffer->rbo);
  		glBindRenderbuffer(GL_RENDERBUFFER, buffer->rbo);
  		renderer->procs.glEGLImageTargetRenderbufferStorageOES(GL_RENDERBUFFER,
  			buffer->image);
  		glBindRenderbuffer(GL_RENDERBUFFER, 0);
  
  		glGenFramebuffers(1, &buffer->fbo);
  		glBindFramebuffer(GL_FRAMEBUFFER, buffer->fbo);
  		glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
  			GL_RENDERBUFFER, buffer->rbo);
  		GLenum fb_status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
  		glBindFramebuffer(GL_FRAMEBUFFER, 0);
  
  		pop_gles2_debug(renderer);
  
  		if (fb_status != GL_FRAMEBUFFER_COMPLETE) {
  			wlr_log(WLR_ERROR, "Failed to create FBO");
  			goto error_image;
  		}
  		wlr_log(WLR_DEBUG, "Created GL FBO for buffer %dx%d",
  			wlr_buffer->width, wlr_buffer->height);
  	}
  
  	buffer->buffer_destroy.notify = handle_buffer_destroy;
  	wl_signal_add(&wlr_buffer->events.destroy, &buffer->buffer_destroy);
  
  	wl_list_insert(&renderer->buffers, &buffer->link);
  
  	return buffer;
  
  error_image:
  	wlr_egl_destroy_image(renderer->egl, buffer->image);
  error_buffer:
  	free(buffer);
  	return NULL;
  }
  
  static bool gles2_bind_buffer(struct wlr_renderer *wlr_renderer,
  		struct wlr_buffer *wlr_buffer) {
  	struct wlr_gles2_renderer *renderer = gles2_get_renderer(wlr_renderer);
  
  	if (renderer->current_buffer != NULL) {
  		assert(wlr_egl_is_current(renderer->egl));
  
  		push_gles2_debug(renderer);
  		glFlush();
  		glBindFramebuffer(GL_FRAMEBUFFER, 0);
  		pop_gles2_debug(renderer);
  
  		wlr_buffer_unlock(renderer->current_buffer->buffer);
  		renderer->current_buffer = NULL;
  	}
  
  	if (wlr_buffer == NULL) {
  		wlr_egl_unset_current(renderer->egl);
  		return true;
  	}
  
  	// Used for setting up current EGL context for a frame.
  	renderer->egl->current_eglstream = wlr_buffer->egl_stream;
  
  	wlr_egl_make_current(renderer->egl);
  
  	struct wlr_gles2_buffer *buffer = get_buffer(renderer, wlr_buffer);
  	if (buffer == NULL) {
  		buffer = create_buffer(renderer, wlr_buffer);
  	}
  	if (buffer == NULL) {
  		return false;
  	}
  
  	wlr_buffer_lock(wlr_buffer);
  	renderer->current_buffer = buffer;
  
  	push_gles2_debug(renderer);
  	glBindFramebuffer(GL_FRAMEBUFFER, renderer->current_buffer->fbo);
  	pop_gles2_debug(renderer);
  
  	return true;
  }
  
  static void gles2_begin(struct wlr_renderer *wlr_renderer, uint32_t width,
  		uint32_t height) {
  	struct wlr_gles2_renderer *renderer =
  		gles2_get_renderer_in_context(wlr_renderer);
  
  	push_gles2_debug(renderer);
  
  	glViewport(0, 0, width, height);
  	renderer->viewport_width = width;
  	renderer->viewport_height = height;
  
  	// refresh projection matrix
  	wlr_matrix_projection(renderer->projection, width, height,
  			WL_OUTPUT_TRANSFORM_NORMAL);
  
  	// enable transparency
  	glEnable(GL_BLEND);
  	glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
  
  	// XXX: maybe we should save output projection and remove some of the need
  	// for users to sling matricies themselves
  
  	pop_gles2_debug(renderer);
  }
  
  static void gles2_end(struct wlr_renderer *wlr_renderer) {
  	gles2_get_renderer_in_context(wlr_renderer);
  	// no-op
  }
  
  static void gles2_clear(struct wlr_renderer *wlr_renderer,
  		const float color[static 4]) {
  	struct wlr_gles2_renderer *renderer =
  		gles2_get_renderer_in_context(wlr_renderer);
  
  	push_gles2_debug(renderer);
  	glClearColor(color[0], color[1], color[2], color[3]);
  	glClear(GL_COLOR_BUFFER_BIT);
  	pop_gles2_debug(renderer);
  }
  
  static void gles2_scissor(struct wlr_renderer *wlr_renderer,
  		struct wlr_box *box) {
  	struct wlr_gles2_renderer *renderer =
  		gles2_get_renderer_in_context(wlr_renderer);
  
  	push_gles2_debug(renderer);
  	if (box != NULL) {
  		glScissor(box->x, box->y, box->width, box->height);
  		glEnable(GL_SCISSOR_TEST);
  	} else {
  		glDisable(GL_SCISSOR_TEST);
  	}
  	pop_gles2_debug(renderer);
  }
  
  static const float flip_180[9] = {
  	1.0f, 0.0f, 0.0f,
  	0.0f, -1.0f, 0.0f,
  	0.0f, 0.0f, 1.0f,
  };
  
  static bool gles2_render_subtexture_with_matrix(
  		struct wlr_renderer *wlr_renderer, struct wlr_texture *wlr_texture,
  		const struct wlr_fbox *box, const float matrix[static 9],
  		float alpha) {
  	struct wlr_gles2_renderer *renderer =
  		gles2_get_renderer_in_context(wlr_renderer);
  	struct wlr_gles2_texture *texture =
  		gles2_get_texture(wlr_texture);
  
  	struct wlr_gles2_tex_shader *shader = NULL;
  	switch (texture->target) {
  	case GL_TEXTURE_2D:
  		if (texture->has_alpha) {
  			shader = &renderer->shaders.tex_rgba;
  		} else {
  			shader = &renderer->shaders.tex_rgbx;
  		}
  		break;
  	case GL_TEXTURE_EXTERNAL_OES:
  		shader = &renderer->shaders.tex_ext;
  
  		if (!renderer->exts.egl_image_external_oes) {
  			wlr_log(WLR_ERROR, "Failed to render texture: "
  				"GL_TEXTURE_EXTERNAL_OES not supported");
  			return false;
  		}
  		break;
  	default:
  		abort();
  	}
  
  	float gl_matrix[9];
  	wlr_matrix_multiply(gl_matrix, renderer->projection, matrix);
  	wlr_matrix_multiply(gl_matrix, flip_180, gl_matrix);
  
  	// OpenGL ES 2 requires the glUniformMatrix3fv transpose parameter to be set
  	// to GL_FALSE
  	wlr_matrix_transpose(gl_matrix, gl_matrix);
  
  	push_gles2_debug(renderer);
  
  	glActiveTexture(GL_TEXTURE0);
  	glBindTexture(texture->target, texture->tex);
  
  	glTexParameteri(texture->target, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  
  	glUseProgram(shader->program);
  
  	glUniformMatrix3fv(shader->proj, 1, GL_FALSE, gl_matrix);
  	glUniform1i(shader->invert_y, texture->inverted_y);
  	glUniform1i(shader->tex, 0);
  	glUniform1f(shader->alpha, alpha);
  
  	const GLfloat x1 = box->x / wlr_texture->width;
  	const GLfloat y1 = box->y / wlr_texture->height;
  	const GLfloat x2 = (box->x + box->width) / wlr_texture->width;
  	const GLfloat y2 = (box->y + box->height) / wlr_texture->height;
  	const GLfloat texcoord[] = {
  		x2, y1, // top right
  		x1, y1, // top left
  		x2, y2, // bottom right
  		x1, y2, // bottom left
  	};
  
  	glVertexAttribPointer(shader->pos_attrib, 2, GL_FLOAT, GL_FALSE, 0, verts);
  	glVertexAttribPointer(shader->tex_attrib, 2, GL_FLOAT, GL_FALSE, 0, texcoord);
  
  	glEnableVertexAttribArray(shader->pos_attrib);
  	glEnableVertexAttribArray(shader->tex_attrib);
  
  	glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
  
  	glDisableVertexAttribArray(shader->pos_attrib);
  	glDisableVertexAttribArray(shader->tex_attrib);
  
  	glBindTexture(texture->target, 0);
  
  	pop_gles2_debug(renderer);
  	return true;
  }
  
  static void gles2_render_quad_with_matrix(struct wlr_renderer *wlr_renderer,
  		const float color[static 4], const float matrix[static 9]) {
  	struct wlr_gles2_renderer *renderer =
  		gles2_get_renderer_in_context(wlr_renderer);
  
  	float gl_matrix[9];
  	wlr_matrix_multiply(gl_matrix, renderer->projection, matrix);
  	wlr_matrix_multiply(gl_matrix, flip_180, gl_matrix);
  
  	// OpenGL ES 2 requires the glUniformMatrix3fv transpose parameter to be set
  	// to GL_FALSE
  	wlr_matrix_transpose(gl_matrix, gl_matrix);
  
  	push_gles2_debug(renderer);
  	glUseProgram(renderer->shaders.quad.program);
  
  	glUniformMatrix3fv(renderer->shaders.quad.proj, 1, GL_FALSE, gl_matrix);
  	glUniform4f(renderer->shaders.quad.color, color[0], color[1], color[2], color[3]);
  
  	glVertexAttribPointer(renderer->shaders.quad.pos_attrib, 2, GL_FLOAT, GL_FALSE,
  			0, verts);
  
  	glEnableVertexAttribArray(renderer->shaders.quad.pos_attrib);
  
  	glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
  
  	glDisableVertexAttribArray(renderer->shaders.quad.pos_attrib);
  
  	pop_gles2_debug(renderer);
  }
  
  static void gles2_render_ellipse_with_matrix(struct wlr_renderer *wlr_renderer,
  		const float color[static 4], const float matrix[static 9]) {
  	struct wlr_gles2_renderer *renderer =
  		gles2_get_renderer_in_context(wlr_renderer);
  
  	float gl_matrix[9];
  	wlr_matrix_multiply(gl_matrix, renderer->projection, matrix);
  	wlr_matrix_multiply(gl_matrix, flip_180, gl_matrix);
  
  	// OpenGL ES 2 requires the glUniformMatrix3fv transpose parameter to be set
  	// to GL_FALSE
  	wlr_matrix_transpose(gl_matrix, gl_matrix);
  
  	static const GLfloat texcoord[] = {
  		1, 0, // top right
  		0, 0, // top left
  		1, 1, // bottom right
  		0, 1, // bottom left
  	};
  
  	push_gles2_debug(renderer);
  	glUseProgram(renderer->shaders.ellipse.program);
  
  	glUniformMatrix3fv(renderer->shaders.ellipse.proj, 1, GL_FALSE, gl_matrix);
  	glUniform4f(renderer->shaders.ellipse.color, color[0], color[1], color[2], color[3]);
  
  	glVertexAttribPointer(renderer->shaders.ellipse.pos_attrib, 2, GL_FLOAT,
  			GL_FALSE, 0, verts);
  	glVertexAttribPointer(renderer->shaders.ellipse.tex_attrib, 2, GL_FLOAT,
  			GL_FALSE, 0, texcoord);
  
  	glEnableVertexAttribArray(renderer->shaders.ellipse.pos_attrib);
  	glEnableVertexAttribArray(renderer->shaders.ellipse.tex_attrib);
  
  	glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
  
  	glDisableVertexAttribArray(renderer->shaders.ellipse.pos_attrib);
  	glDisableVertexAttribArray(renderer->shaders.ellipse.tex_attrib);
  	pop_gles2_debug(renderer);
  }
  
  static const uint32_t *gles2_get_shm_texture_formats(
  		struct wlr_renderer *wlr_renderer, size_t *len) {
  	return get_gles2_shm_formats(len);
  }
  
  static bool gles2_resource_is_wl_drm_buffer(struct wlr_renderer *wlr_renderer,
  		struct wl_resource *resource) {
  	struct wlr_gles2_renderer *renderer = gles2_get_renderer(wlr_renderer);
  
  	if (!renderer->egl->exts.bind_wayland_display_wl) {
  		return false;
  	}
  
  	EGLint fmt;
  	return renderer->egl->procs.eglQueryWaylandBufferWL(renderer->egl->display,
  		resource, EGL_TEXTURE_FORMAT, &fmt);
  }
  
  static void gles2_wl_drm_buffer_get_size(struct wlr_renderer *wlr_renderer,
  		struct wl_resource *buffer, int *width, int *height) {
  	struct wlr_gles2_renderer *renderer =
  		gles2_get_renderer(wlr_renderer);
  
  	if (!renderer->egl->exts.bind_wayland_display_wl) {
  		return;
  	}
  
  	renderer->egl->procs.eglQueryWaylandBufferWL(renderer->egl->display,
  		buffer, EGL_WIDTH, width);
  	renderer->egl->procs.eglQueryWaylandBufferWL(renderer->egl->display,
  		buffer, EGL_HEIGHT, height);
  }
  
  static const struct wlr_drm_format_set *gles2_get_dmabuf_texture_formats(
  		struct wlr_renderer *wlr_renderer) {
  	struct wlr_gles2_renderer *renderer = gles2_get_renderer(wlr_renderer);
  	return wlr_egl_get_dmabuf_texture_formats(renderer->egl);
  }
  
  static const struct wlr_drm_format_set *gles2_get_dmabuf_render_formats(
  		struct wlr_renderer *wlr_renderer) {
  	struct wlr_gles2_renderer *renderer = gles2_get_renderer(wlr_renderer);
  	return wlr_egl_get_dmabuf_render_formats(renderer->egl);
  }
  
  static uint32_t gles2_preferred_read_format(
  		struct wlr_renderer *wlr_renderer) {
  	struct wlr_gles2_renderer *renderer =
  		gles2_get_renderer_in_context(wlr_renderer);
  
  	push_gles2_debug(renderer);
  
  	GLint gl_format = -1, gl_type = -1;
  	glGetIntegerv(GL_IMPLEMENTATION_COLOR_READ_FORMAT, &gl_format);
  	glGetIntegerv(GL_IMPLEMENTATION_COLOR_READ_TYPE, &gl_type);
  
  	EGLint alpha_size = -1;
  	glBindRenderbuffer(GL_RENDERBUFFER, renderer->current_buffer->rbo);
  	glGetRenderbufferParameteriv(GL_RENDERBUFFER,
  		GL_RENDERBUFFER_ALPHA_SIZE, &alpha_size);
  	glBindRenderbuffer(GL_RENDERBUFFER, 0);
  
  	pop_gles2_debug(renderer);
  
  	const struct wlr_gles2_pixel_format *fmt =
  		get_gles2_format_from_gl(gl_format, gl_type, alpha_size > 0);
  	if (fmt != NULL) {
  		return fmt->drm_format;
  	}
  
  	if (renderer->exts.read_format_bgra_ext) {
  		return DRM_FORMAT_XRGB8888;
  	}
  	return DRM_FORMAT_XBGR8888;
  }
  
  static bool gles2_read_pixels(struct wlr_renderer *wlr_renderer,
  		uint32_t drm_format, uint32_t *flags, uint32_t stride,
  		uint32_t width, uint32_t height, uint32_t src_x, uint32_t src_y,
  		uint32_t dst_x, uint32_t dst_y, void *data) {
  	struct wlr_gles2_renderer *renderer =
  		gles2_get_renderer_in_context(wlr_renderer);
  
  	const struct wlr_gles2_pixel_format *fmt =
  		get_gles2_format_from_drm(drm_format);
  	if (fmt == NULL) {
  		wlr_log(WLR_ERROR, "Cannot read pixels: unsupported pixel format");
  		return false;
  	}
  
  	if (fmt->gl_format == GL_BGRA_EXT && !renderer->exts.read_format_bgra_ext) {
  		wlr_log(WLR_ERROR,
  			"Cannot read pixels: missing GL_EXT_read_format_bgra extension");
  		return false;
  	}
  
  	push_gles2_debug(renderer);
  
  	// Make sure any pending drawing is finished before we try to read it
  	glFinish();
  
  	glGetError(); // Clear the error flag
  
  	unsigned char *p = (unsigned char *)data + dst_y * stride;
  	uint32_t pack_stride = width * fmt->bpp / 8;
  	if (pack_stride == stride && dst_x == 0) {
  		// Under these particular conditions, we can read the pixels with only
  		// one glReadPixels call
  
  		glReadPixels(src_x, src_y, width, height, fmt->gl_format, fmt->gl_type, p);
  	} else {
  		// Unfortunately GLES2 doesn't support GL_PACK_*, so we have to read
  		// the lines out row by row
  		for (size_t i = 0; i < height; ++i) {
  			uint32_t y = src_y + i;
  			glReadPixels(src_x, y, width, 1, fmt->gl_format,
  				fmt->gl_type, p + i * stride + dst_x * fmt->bpp / 8);
  		}
  	}
  
  	pop_gles2_debug(renderer);
  
  	if (flags != NULL) {
  		*flags = 0;
  	}
  
  	return glGetError() == GL_NO_ERROR;
  }
  
  static bool gles2_blit_dmabuf(struct wlr_renderer *wlr_renderer,
  		struct wlr_dmabuf_attributes *dst_attr,
  		struct wlr_dmabuf_attributes *src_attr) {
  	struct wlr_gles2_renderer *renderer = gles2_get_renderer(wlr_renderer);
  	if (!renderer->procs.glEGLImageTargetRenderbufferStorageOES) {
  		return false;
  	}
  
  	if(!renderer->egl->gbm_device) {
  		// gdm_device is null for EGLStreams mode.
  		// TODO: Blitting for EGLStreams if required.
  		// TODO(danvd): Test with 2 GPU combinations (I've got some).
  		// Note: This will be greatly simplified when nvidia 
  		// dms-buf support is ready.
  		return false;
  	}
  
  	struct wlr_egl_context old_context;
  	wlr_egl_save_context(&old_context);
  
  	bool r = false;
  	struct wlr_texture *src_tex =
  		wlr_texture_from_dmabuf(wlr_renderer, src_attr);
  	if (!src_tex) {
  		goto restore_context_out;
  	}
  
  	// TODO: get inverted_y right
  	// This is to take into account y-inversion on both buffers rather than
  	// just the source buffer.
  	bool src_inverted_y =
  		!!(src_attr->flags & WLR_DMABUF_ATTRIBUTES_FLAGS_Y_INVERT);
  	bool dst_inverted_y =
  		!!(dst_attr->flags & WLR_DMABUF_ATTRIBUTES_FLAGS_Y_INVERT);
  	struct wlr_gles2_texture *gles2_src_tex = gles2_get_texture(src_tex);
  	gles2_src_tex->inverted_y = src_inverted_y ^ dst_inverted_y;
  
  	if (!wlr_egl_make_current(renderer->egl)) {
  		goto texture_destroy_out;
  	}
  
  	// TODO: The imported buffer should be checked with
  	// eglQueryDmaBufModifiersEXT to see if it may be modified.
  	bool external_only = false;
  	EGLImageKHR image = wlr_egl_create_image_from_dmabuf(renderer->egl, dst_attr,
  			&external_only);
  	if (image == EGL_NO_IMAGE_KHR) {
  		goto texture_destroy_out;
  	}
  
  	GLuint rbo = 0;
  	glGenRenderbuffers(1, &rbo);
  	glBindRenderbuffer(GL_RENDERBUFFER, rbo);
  	renderer->procs.glEGLImageTargetRenderbufferStorageOES(GL_RENDERBUFFER,
  			image);
  	glBindRenderbuffer(GL_RENDERBUFFER, 0);
  
  	GLuint fbo = 0;
  	glGenFramebuffers(1, &fbo);
  	glBindFramebuffer(GL_FRAMEBUFFER, fbo);
  	glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
  			GL_RENDERBUFFER, rbo);
  
  	GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
  	if (status != GL_FRAMEBUFFER_COMPLETE) {
  		goto out;
  	}
  
  	// TODO: use ANGLE_framebuffer_blit if available
  	float mat[9];
  	wlr_matrix_identity(mat);
  
  	wlr_renderer_begin(wlr_renderer, dst_attr->width, dst_attr->height);
  	wlr_renderer_clear(wlr_renderer, (float[]){ 0.0, 0.0, 0.0, 0.0 });
  	wlr_render_texture_with_matrix(wlr_renderer, src_tex, mat, 1.0f);
  	wlr_renderer_end(wlr_renderer);
  
  	r = true;
  out:
  	glBindFramebuffer(GL_FRAMEBUFFER, 0);
  	glDeleteFramebuffers(1, &fbo);
  	glDeleteRenderbuffers(1, &rbo);
  	wlr_egl_destroy_image(renderer->egl, image);
  texture_destroy_out:
  	wlr_texture_destroy(src_tex);
  restore_context_out:
  	wlr_egl_restore_context(&old_context);
  	return r;
  }
  
  static bool gles2_init_wl_display(struct wlr_renderer *wlr_renderer,
  		struct wl_display *wl_display) {
  	struct wlr_gles2_renderer *renderer =
  		gles2_get_renderer(wlr_renderer);
  
  	if (renderer->egl->exts.bind_wayland_display_wl) {
  		if (!wlr_egl_bind_display(renderer->egl, wl_display)) {
  			wlr_log(WLR_ERROR, "Failed to bind wl_display to EGL");
  			return false;
  		}
  	} else {
  		wlr_log(WLR_INFO, "EGL_WL_bind_wayland_display is not supported");
  	}
  
  	if (renderer->egl->exts.image_dmabuf_import_ext) {
  		if (wlr_linux_dmabuf_v1_create(wl_display, wlr_renderer) == NULL) {
  			return false;
  		}
  	} else {
  		wlr_log(WLR_INFO, "EGL_EXT_image_dma_buf_import is not supported");
  	}
  
  	return true;
  }
  
  static int gles2_get_drm_fd(struct wlr_renderer *wlr_renderer) {
  	struct wlr_gles2_renderer *renderer =
  		gles2_get_renderer(wlr_renderer);
  
  	if (renderer->drm_fd < 0) {
  		renderer->drm_fd = wlr_egl_dup_drm_fd(renderer->egl);
  	}
  
  	return renderer->drm_fd;
  }
  
  struct wlr_egl *gles2_renderer_get_egl(struct wlr_renderer *wlr_renderer) {
  	struct wlr_gles2_renderer *renderer =
  		gles2_get_renderer(wlr_renderer);
  	return renderer->egl;
  }
  
  static void gles2_destroy(struct wlr_renderer *wlr_renderer) {
  	struct wlr_gles2_renderer *renderer = gles2_get_renderer(wlr_renderer);
  
  	wlr_egl_make_current(renderer->egl);
  
  	struct wlr_gles2_buffer *buffer, *buffer_tmp;
  	wl_list_for_each_safe(buffer, buffer_tmp, &renderer->buffers, link) {
  		destroy_buffer(buffer);
  	}
  
  	push_gles2_debug(renderer);
  	glDeleteProgram(renderer->shaders.quad.program);
  	glDeleteProgram(renderer->shaders.ellipse.program);
  	glDeleteProgram(renderer->shaders.tex_rgba.program);
  	glDeleteProgram(renderer->shaders.tex_rgbx.program);
  	glDeleteProgram(renderer->shaders.tex_ext.program);
  	pop_gles2_debug(renderer);
  
  	if (renderer->exts.debug_khr) {
  		glDisable(GL_DEBUG_OUTPUT_KHR);
  		renderer->procs.glDebugMessageCallbackKHR(NULL, NULL);
  	}
  
  	wlr_egl_unset_current(renderer->egl);
  	wlr_egl_destroy(renderer->egl);
  
  	if (renderer->drm_fd >= 0) {
  		close(renderer->drm_fd);
  	}
  
  	free(renderer);
  }
  
  static const struct wlr_renderer_impl renderer_impl = {
  	.destroy = gles2_destroy,
  	.bind_buffer = gles2_bind_buffer,
  	.begin = gles2_begin,
  	.end = gles2_end,
  	.clear = gles2_clear,
  	.scissor = gles2_scissor,
  	.render_subtexture_with_matrix = gles2_render_subtexture_with_matrix,
  	.render_quad_with_matrix = gles2_render_quad_with_matrix,
  	.render_ellipse_with_matrix = gles2_render_ellipse_with_matrix,
  	.get_shm_texture_formats = gles2_get_shm_texture_formats,
  	.resource_is_wl_drm_buffer = gles2_resource_is_wl_drm_buffer,
  	.wl_drm_buffer_get_size = gles2_wl_drm_buffer_get_size,
  	.get_dmabuf_texture_formats = gles2_get_dmabuf_texture_formats,
  	.get_dmabuf_render_formats = gles2_get_dmabuf_render_formats,
  	.preferred_read_format = gles2_preferred_read_format,
  	.read_pixels = gles2_read_pixels,
  	.texture_from_pixels = gles2_texture_from_pixels,
  	.texture_from_wl_drm = gles2_texture_from_wl_drm,
  	.texture_from_dmabuf = gles2_texture_from_dmabuf,
  	.init_wl_display = gles2_init_wl_display,
  	.blit_dmabuf = gles2_blit_dmabuf,
  	.get_drm_fd = gles2_get_drm_fd,
  	.texture_from_wl_eglstream = gles2_texture_from_wl_eglstream,
  	.get_egl = gles2_renderer_get_egl
  };
  
  void push_gles2_debug_(struct wlr_gles2_renderer *renderer,
  		const char *file, const char *func) {
  	if (!renderer->procs.glPushDebugGroupKHR) {
  		return;
  	}
  
  	int len = snprintf(NULL, 0, "%s:%s", file, func) + 1;
  	char str[len];
  	snprintf(str, len, "%s:%s", file, func);
  	renderer->procs.glPushDebugGroupKHR(GL_DEBUG_SOURCE_APPLICATION_KHR, 1, -1, str);
  }
  
  void pop_gles2_debug(struct wlr_gles2_renderer *renderer) {
  	if (renderer->procs.glPopDebugGroupKHR) {
  		renderer->procs.glPopDebugGroupKHR();
  	}
  }
  
  static enum wlr_log_importance gles2_log_importance_to_wlr(GLenum type) {
  	switch (type) {
  	case GL_DEBUG_TYPE_ERROR_KHR:               return WLR_ERROR;
  	case GL_DEBUG_TYPE_DEPRECATED_BEHAVIOR_KHR: return WLR_DEBUG;
  	case GL_DEBUG_TYPE_UNDEFINED_BEHAVIOR_KHR:  return WLR_ERROR;
  	case GL_DEBUG_TYPE_PORTABILITY_KHR:         return WLR_DEBUG;
  	case GL_DEBUG_TYPE_PERFORMANCE_KHR:         return WLR_DEBUG;
  	case GL_DEBUG_TYPE_OTHER_KHR:               return WLR_DEBUG;
  	case GL_DEBUG_TYPE_MARKER_KHR:              return WLR_DEBUG;
  	case GL_DEBUG_TYPE_PUSH_GROUP_KHR:          return WLR_DEBUG;
  	case GL_DEBUG_TYPE_POP_GROUP_KHR:           return WLR_DEBUG;
  	default:                                    return WLR_DEBUG;
  	}
  }
  
  static void gles2_log(GLenum src, GLenum type, GLuint id, GLenum severity,
  		GLsizei len, const GLchar *msg, const void *user) {
  	_wlr_log(gles2_log_importance_to_wlr(type), "[GLES2] %s", msg);
  }
  
  static GLuint compile_shader(struct wlr_gles2_renderer *renderer,
  		GLuint type, const GLchar *src) {
  	push_gles2_debug(renderer);
  
  	GLuint shader = glCreateShader(type);
  	glShaderSource(shader, 1, &src, NULL);
  	glCompileShader(shader);
  
  	GLint ok;
  	glGetShaderiv(shader, GL_COMPILE_STATUS, &ok);
  	if (ok == GL_FALSE) {
  		glDeleteShader(shader);
  		shader = 0;
  	}
  
  	pop_gles2_debug(renderer);
  	return shader;
  }
  
  static GLuint link_program(struct wlr_gles2_renderer *renderer,
  		const GLchar *vert_src, const GLchar *frag_src) {
  	push_gles2_debug(renderer);
  
  	GLuint vert = compile_shader(renderer, GL_VERTEX_SHADER, vert_src);
  	if (!vert) {
  		goto error;
  	}
  
  	GLuint frag = compile_shader(renderer, GL_FRAGMENT_SHADER, frag_src);
  	if (!frag) {
  		glDeleteShader(vert);
  		goto error;
  	}
  
  	GLuint prog = glCreateProgram();
  	glAttachShader(prog, vert);
  	glAttachShader(prog, frag);
  	glLinkProgram(prog);
  
  	glDetachShader(prog, vert);
  	glDetachShader(prog, frag);
  	glDeleteShader(vert);
  	glDeleteShader(frag);
  
  	GLint ok;
  	glGetProgramiv(prog, GL_LINK_STATUS, &ok);
  	if (ok == GL_FALSE) {
  		glDeleteProgram(prog);
  		goto error;
  	}
  
  	pop_gles2_debug(renderer);
  	return prog;
  
  error:
  	pop_gles2_debug(renderer);
  	return 0;
  }
  
  static bool check_gl_ext(const char *exts, const char *ext) {
  	size_t extlen = strlen(ext);
  	const char *end = exts + strlen(exts);
  
  	while (exts < end) {
  		if (exts[0] == ' ') {
  			exts++;
  			continue;
  		}
  		size_t n = strcspn(exts, " ");
  		if (n == extlen && strncmp(ext, exts, n) == 0) {
  			return true;
  		}
  		exts += n;
  	}
  	return false;
  }
  
  static void load_gl_proc(void *proc_ptr, const char *name) {
  	void *proc = (void *)eglGetProcAddress(name);
  	if (proc == NULL) {
  		wlr_log(WLR_ERROR, "eglGetProcAddress(%s) failed", name);
  		abort();
  	}
  	*(void **)proc_ptr = proc;
  }
  
  extern const GLchar quad_vertex_src[];
  extern const GLchar quad_fragment_src[];
  extern const GLchar ellipse_fragment_src[];
  extern const GLchar tex_vertex_src[];
  extern const GLchar tex_fragment_src_rgba[];
  extern const GLchar tex_fragment_src_rgbx[];
  extern const GLchar tex_fragment_src_external[];
  
  struct wlr_renderer *wlr_gles2_renderer_create(struct wlr_egl *egl) {
  	if (!wlr_egl_make_current(egl)) {
  		return NULL;
  	}
  
  	const char *exts_str = (const char *)glGetString(GL_EXTENSIONS);
  	if (exts_str == NULL) {
  		wlr_log(WLR_ERROR, "Failed to get GL_EXTENSIONS");
  		return NULL;
  	}
  
  	struct wlr_gles2_renderer *renderer =
  		calloc(1, sizeof(struct wlr_gles2_renderer));
  	if (renderer == NULL) {
  		return NULL;
  	}
  	wlr_renderer_init(&renderer->wlr_renderer, &renderer_impl);
  
  	wl_list_init(&renderer->buffers);
  	wl_list_init(&renderer->client_streams);
  
  	renderer->egl = egl;
  	renderer->exts_str = exts_str;
  	renderer->drm_fd = -1;
  
  	wlr_log(WLR_INFO, "Using %s", glGetString(GL_VERSION));
  	wlr_log(WLR_INFO, "GL vendor: %s", glGetString(GL_VENDOR));
  	wlr_log(WLR_INFO, "GL renderer: %s", glGetString(GL_RENDERER));
  	wlr_log(WLR_INFO, "Supported GLES2 extensions: %s", exts_str);
  
  	if (!check_gl_ext(exts_str, "GL_EXT_texture_format_BGRA8888")) {
  		wlr_log(WLR_ERROR, "BGRA8888 format not supported by GLES2");
  		free(renderer);
  		return NULL;
  	}
  	if (!check_gl_ext(exts_str, "GL_EXT_unpack_subimage")) {
  		wlr_log(WLR_ERROR, "GL_EXT_unpack_subimage not supported");
  		free(renderer);
  		return NULL;
  	}
  
  	renderer->exts.read_format_bgra_ext =
  		check_gl_ext(exts_str, "GL_EXT_read_format_bgra");
  
  	if (check_gl_ext(exts_str, "GL_KHR_debug")) {
  		renderer->exts.debug_khr = true;
  		load_gl_proc(&renderer->procs.glDebugMessageCallbackKHR,
  			"glDebugMessageCallbackKHR");
  		load_gl_proc(&renderer->procs.glDebugMessageControlKHR,
  			"glDebugMessageControlKHR");
  	}
  
  	if (check_gl_ext(exts_str, "GL_OES_EGL_image_external")) {
  		renderer->exts.egl_image_external_oes = true;
  		load_gl_proc(&renderer->procs.glEGLImageTargetTexture2DOES,
  			"glEGLImageTargetTexture2DOES");
  	}
  
  	if (check_gl_ext(exts_str, "GL_OES_EGL_image")) {
  		renderer->exts.egl_image_oes = true;
  		load_gl_proc(&renderer->procs.glEGLImageTargetRenderbufferStorageOES,
  			"glEGLImageTargetRenderbufferStorageOES");
  	}
  
  	if (renderer->exts.debug_khr) {
  		glEnable(GL_DEBUG_OUTPUT_KHR);
  		glEnable(GL_DEBUG_OUTPUT_SYNCHRONOUS_KHR);
  		renderer->procs.glDebugMessageCallbackKHR(gles2_log, NULL);
  
  		// Silence unwanted message types
  		renderer->procs.glDebugMessageControlKHR(GL_DONT_CARE,
  			GL_DEBUG_TYPE_POP_GROUP_KHR, GL_DONT_CARE, 0, NULL, GL_FALSE);
  		renderer->procs.glDebugMessageControlKHR(GL_DONT_CARE,
  			GL_DEBUG_TYPE_PUSH_GROUP_KHR, GL_DONT_CARE, 0, NULL, GL_FALSE);
  	}
  
  	push_gles2_debug(renderer);
  
  	GLuint prog;
  	renderer->shaders.quad.program = prog =
  		link_program(renderer, quad_vertex_src, quad_fragment_src);
  	if (!renderer->shaders.quad.program) {
  		goto error;
  	}
  	renderer->shaders.quad.proj = glGetUniformLocation(prog, "proj");
  	renderer->shaders.quad.color = glGetUniformLocation(prog, "color");
  	renderer->shaders.quad.pos_attrib = glGetAttribLocation(prog, "pos");
  
  	renderer->shaders.ellipse.program = prog =
  		link_program(renderer, quad_vertex_src, ellipse_fragment_src);
  	if (!renderer->shaders.ellipse.program) {
  		goto error;
  	}
  	renderer->shaders.ellipse.proj = glGetUniformLocation(prog, "proj");
  	renderer->shaders.ellipse.color = glGetUniformLocation(prog, "color");
  	renderer->shaders.ellipse.pos_attrib = glGetAttribLocation(prog, "pos");
  	renderer->shaders.ellipse.tex_attrib = glGetAttribLocation(prog, "texcoord");
  
  	renderer->shaders.tex_rgba.program = prog =
  		link_program(renderer, tex_vertex_src, tex_fragment_src_rgba);
  	if (!renderer->shaders.tex_rgba.program) {
  		goto error;
  	}
  	renderer->shaders.tex_rgba.proj = glGetUniformLocation(prog, "proj");
  	renderer->shaders.tex_rgba.invert_y = glGetUniformLocation(prog, "invert_y");
  	renderer->shaders.tex_rgba.tex = glGetUniformLocation(prog, "tex");
  	renderer->shaders.tex_rgba.alpha = glGetUniformLocation(prog, "alpha");
  	renderer->shaders.tex_rgba.pos_attrib = glGetAttribLocation(prog, "pos");
  	renderer->shaders.tex_rgba.tex_attrib = glGetAttribLocation(prog, "texcoord");
  
  	renderer->shaders.tex_rgbx.program = prog =
  		link_program(renderer, tex_vertex_src, tex_fragment_src_rgbx);
  	if (!renderer->shaders.tex_rgbx.program) {
  		goto error;
  	}
  	renderer->shaders.tex_rgbx.proj = glGetUniformLocation(prog, "proj");
  	renderer->shaders.tex_rgbx.invert_y = glGetUniformLocation(prog, "invert_y");
  	renderer->shaders.tex_rgbx.tex = glGetUniformLocation(prog, "tex");
  	renderer->shaders.tex_rgbx.alpha = glGetUniformLocation(prog, "alpha");
  	renderer->shaders.tex_rgbx.pos_attrib = glGetAttribLocation(prog, "pos");
  	renderer->shaders.tex_rgbx.tex_attrib = glGetAttribLocation(prog, "texcoord");
  
  	if (renderer->exts.egl_image_external_oes) {
  		renderer->shaders.tex_ext.program = prog =
  			link_program(renderer, tex_vertex_src, tex_fragment_src_external);
  		if (!renderer->shaders.tex_ext.program) {
  			goto error;
  		}
  		renderer->shaders.tex_ext.proj = glGetUniformLocation(prog, "proj");
  		renderer->shaders.tex_ext.invert_y = glGetUniformLocation(prog, "invert_y");
  		renderer->shaders.tex_ext.tex = glGetUniformLocation(prog, "tex");
  		renderer->shaders.tex_ext.alpha = glGetUniformLocation(prog, "alpha");
  		renderer->shaders.tex_ext.pos_attrib = glGetAttribLocation(prog, "pos");
  		renderer->shaders.tex_ext.tex_attrib = glGetAttribLocation(prog, "texcoord");
  	}
  
  	pop_gles2_debug(renderer);
  
  	wlr_egl_unset_current(renderer->egl);
  
  	return &renderer->wlr_renderer;
  
  error:
  	glDeleteProgram(renderer->shaders.quad.program);
  	glDeleteProgram(renderer->shaders.ellipse.program);
  	glDeleteProgram(renderer->shaders.tex_rgba.program);
  	glDeleteProgram(renderer->shaders.tex_rgbx.program);
  	glDeleteProgram(renderer->shaders.tex_ext.program);
  
  	pop_gles2_debug(renderer);
  
  	if (renderer->exts.debug_khr) {
  		glDisable(GL_DEBUG_OUTPUT_KHR);
  		renderer->procs.glDebugMessageCallbackKHR(NULL, NULL);
  	}
  
  	wlr_egl_unset_current(renderer->egl);
  
  	free(renderer);
  	return NULL;
  }
  
  bool wlr_gles2_renderer_check_ext(struct wlr_renderer *wlr_renderer,
  		const char *ext) {
  	struct wlr_gles2_renderer *renderer = gles2_get_renderer(wlr_renderer);
  	return check_gl_ext(renderer->exts_str, ext);
  }
  