output: improve transform matrix calculation

Compute only the transform matrix in the output. The projection matrix
will be calculated inside the gles2 renderer when we start rendering.

The goal is to help the pixman rendering process.

include/render/gles2.h

@@ -34,6 +34,7 @@ struct wlr_gles2_tex_shader {
 struct wlr_gles2_renderer {
 	struct wlr_renderer wlr_renderer;
 
+	float projection[9];
 	struct wlr_egl *egl;
 	int drm_fd;
 

render/gles2/renderer.c

@@ -191,6 +191,10 @@ static void gles2_begin(struct wlr_renderer *wlr_renderer, uint32_t width,
 	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);
@@ -271,7 +275,8 @@ static bool gles2_render_subtexture_with_matrix(
 	}
 
 	float gl_matrix[9];
-	wlr_matrix_multiply(gl_matrix, flip_180, matrix);
+	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
@@ -325,7 +330,8 @@ static void gles2_render_quad_with_matrix(struct wlr_renderer *wlr_renderer,
 		gles2_get_renderer_in_context(wlr_renderer);
 
 	float gl_matrix[9];
-	wlr_matrix_multiply(gl_matrix, flip_180, matrix);
+	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
@@ -355,7 +361,8 @@ static void gles2_render_ellipse_with_matrix(struct wlr_renderer *wlr_renderer,
 		gles2_get_renderer_in_context(wlr_renderer);
 
 	float gl_matrix[9];
-	wlr_matrix_multiply(gl_matrix, flip_180, matrix);
+	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

types/wlr_output.c

@@ -141,8 +141,15 @@ void wlr_output_update_enabled(struct wlr_output *output, bool enabled) {
 }
 
 static void output_update_matrix(struct wlr_output *output) {
-	wlr_matrix_projection(output->transform_matrix, output->width,
-		output->height, output->transform);
+	float width = output->width / 2.f;
+	float height = output->height / 2.f;
+
+	wlr_matrix_identity(output->transform_matrix);
+	if (output->transform != WL_OUTPUT_TRANSFORM_NORMAL) {
+		wlr_matrix_translate(output->transform_matrix, width, height);
+		wlr_matrix_transform(output->transform_matrix, output->transform);
+		wlr_matrix_translate(output->transform_matrix, -width, -height);
+	}
 }
 
 void wlr_output_enable(struct wlr_output *output, bool enable) {