render: add wlr_render_subtexture_with_matrix

This renders only a subset of the texture, instead of the full texture.

include/wlr/render/interface.h

@@ -32,9 +32,9 @@ struct wlr_renderer_impl {
 	void (*end)(struct wlr_renderer *renderer);
 	void (*clear)(struct wlr_renderer *renderer, const float color[static 4]);
 	void (*scissor)(struct wlr_renderer *renderer, struct wlr_box *box);
-	bool (*render_texture_with_matrix)(struct wlr_renderer *renderer,
-		struct wlr_texture *texture, const float matrix[static 9],
-		float alpha);
+	bool (*render_subtexture_with_matrix)(struct wlr_renderer *renderer,
+		struct wlr_texture *texture, const struct wlr_texture_box *box,
+		const float matrix[static 9], float alpha);
 	void (*render_quad_with_matrix)(struct wlr_renderer *renderer,
 		const float color[static 4], const float matrix[static 9]);
 	void (*render_ellipse_with_matrix)(struct wlr_renderer *renderer,

include/wlr/render/wlr_renderer.h

@@ -32,6 +32,11 @@ struct wlr_renderer {
 	} events;
 };
 
+struct wlr_texture_box {
+	float x, y;
+	float width, height;
+};
+
 struct wlr_renderer *wlr_renderer_autocreate(struct wlr_egl *egl, EGLenum platform,
 	void *remote_display, EGLint *config_attribs, EGLint visual_id);
 
@@ -54,6 +59,13 @@ bool wlr_render_texture(struct wlr_renderer *r, struct wlr_texture *texture,
  */
 bool wlr_render_texture_with_matrix(struct wlr_renderer *r,
 	struct wlr_texture *texture, const float matrix[static 9], float alpha);
+/**
+ * Renders the requested texture using the provided matrix, after cropping it
+ * to the provided rectangle.
+ */
+bool wlr_render_subtexture_with_matrix(struct wlr_renderer *r,
+	struct wlr_texture *texture, const struct wlr_texture_box *box,
+	const float matrix[static 9], float alpha);
 /**
  * Renders a solid rectangle in the specified color.
  */

include/wlr/types/wlr_surface.h

@@ -42,10 +42,16 @@ struct wlr_surface_state {
 	int width, height; // in surface-local coordinates
 	int buffer_width, buffer_height;
 
+	/**
+	 * The viewport is applied after the surface transform and scale.
+	 *
+	 * If has_src is true, the surface content is cropped to the provided
+	 * rectangle.
+	 */
 	struct {
 		bool has_src, has_dst;
 		double src_x, src_y, src_width, src_height;
-		int dst_width, dst_height;
+		int dst_width, dst_height; // in surface-local coordinates
 	} viewport;
 
 	struct wl_listener buffer_destroy;

render/gles2/renderer.c

@@ -86,18 +86,19 @@ static void gles2_scissor(struct wlr_renderer *wlr_renderer,
 	POP_GLES2_DEBUG;
 }
 
-static void draw_quad(void) {
+static void draw_quad_with_texcoord(GLfloat x1, GLfloat y1,
+		GLfloat x2, GLfloat y2) {
 	GLfloat verts[] = {
 		1, 0, // top right
 		0, 0, // top left
 		1, 1, // bottom right
 		0, 1, // bottom left
 	};
 	GLfloat texcoord[] = {
-		1, 0, // top right
-		0, 0, // top left
-		1, 1, // bottom right
-		0, 1, // bottom left
+		x2, y1, // top right
+		x1, y1, // top left
+		x2, y2, // bottom right
+		x1, y2, // bottom left
 	};
 
 	glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, verts);
@@ -112,8 +113,13 @@ static void draw_quad(void) {
 	glDisableVertexAttribArray(1);
 }
 
-static bool gles2_render_texture_with_matrix(struct wlr_renderer *wlr_renderer,
-		struct wlr_texture *wlr_texture, const float matrix[static 9],
+static void draw_quad(void) {
+	draw_quad_with_texcoord(0, 0, 1, 1);
+}
+
+static bool gles2_render_subtexture_with_matrix(
+		struct wlr_renderer *wlr_renderer, struct wlr_texture *wlr_texture,
+		const struct wlr_texture_box *box, const float matrix[static 9],
 		float alpha) {
 	struct wlr_gles2_renderer *renderer =
 		gles2_get_renderer_in_context(wlr_renderer);
@@ -162,7 +168,11 @@ static bool gles2_render_texture_with_matrix(struct wlr_renderer *wlr_renderer,
 	glUniform1i(shader->tex, 0);
 	glUniform1f(shader->alpha, alpha);
 
-	draw_quad();
+	GLfloat x1 = box->x / wlr_texture->width;
+	GLfloat y1 = box->y / wlr_texture->height;
+	GLfloat x2 = (box->x + box->width) / wlr_texture->width;
+	GLfloat y2 = (box->y + box->height) / wlr_texture->height;
+	draw_quad_with_texcoord(x1, y1, x2, y2);
 
 	glBindTexture(texture->target, 0);
 
@@ -412,7 +422,7 @@ static const struct wlr_renderer_impl renderer_impl = {
 	.end = gles2_end,
 	.clear = gles2_clear,
 	.scissor = gles2_scissor,
-	.render_texture_with_matrix = gles2_render_texture_with_matrix,
+	.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,
 	.formats = gles2_renderer_formats,

render/wlr_renderer.c

@@ -13,7 +13,7 @@ void wlr_renderer_init(struct wlr_renderer *renderer,
 	assert(impl->begin);
 	assert(impl->clear);
 	assert(impl->scissor);
-	assert(impl->render_texture_with_matrix);
+	assert(impl->render_subtexture_with_matrix);
 	assert(impl->render_quad_with_matrix);
 	assert(impl->render_ellipse_with_matrix);
 	assert(impl->formats);
@@ -80,8 +80,21 @@ bool wlr_render_texture(struct wlr_renderer *r, struct wlr_texture *texture,
 bool wlr_render_texture_with_matrix(struct wlr_renderer *r,
 		struct wlr_texture *texture, const float matrix[static 9],
 		float alpha) {
+	struct wlr_texture_box box = {
+		.x = 0,
+		.y = 0,
+		.width = texture->width,
+		.height = texture->height,
+	};
+	return wlr_render_subtexture_with_matrix(r, texture, &box, matrix, alpha);
+}
+
+bool wlr_render_subtexture_with_matrix(struct wlr_renderer *r,
+		struct wlr_texture *texture, const struct wlr_texture_box *box,
+		const float matrix[static 9], float alpha) {
 	assert(r->rendering);
-	return r->impl->render_texture_with_matrix(r, texture, matrix, alpha);
+	return r->impl->render_subtexture_with_matrix(r, texture,
+		box, matrix, alpha);
 }
 
 void wlr_render_rect(struct wlr_renderer *r, const struct wlr_box *box,