pixman-renderer: simplify the output-to-buffer matrix computation

Now that we have a buffer-to-surface matrix and the global-to-output matrix
is in pixels, we can remove a large chunk of confusing code from the pixman
renderer.  Hopefully, having this stuff in weston core will keep the pixman
renderer from gettin broken quite as often.

This patch makes attempting zoom on the pixman-renderer render funny
stuff. We didn't support zoom before, now it renders wrong instead of
not zooming at all.

[Pekka: adjust commit message]
Tested-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-By: Derek Foreman <derekf@osg.samsung.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/pixman-renderer.c

@@ -140,32 +140,20 @@ region_global_to_output(struct weston_output *output, pixman_region32_t *region)
 #define D2F(v) pixman_double_to_fixed((double)v)
 
 static void
-transform_apply_viewport(pixman_transform_t *transform,
+weston_matrix_to_pixman_transform(pixman_transform_t *pt,
-			 struct weston_surface *surface)
+				  const struct weston_matrix *wm)
 {
-	struct weston_buffer_viewport *vp = &surface->buffer_viewport;
+	/* Pixman supports only 2D transform matrix, but Weston uses 3D, *
-	double src_width, src_height;
+	 * so we're omitting Z coordinate here. */
-	double src_x, src_y;
+	pt->matrix[0][0] = pixman_double_to_fixed(wm->d[0]);
-
+	pt->matrix[0][1] = pixman_double_to_fixed(wm->d[4]);
-	if (vp->buffer.src_width == wl_fixed_from_int(-1)) {
+	pt->matrix[0][2] = pixman_double_to_fixed(wm->d[12]);
-		if (vp->surface.width == -1)
+	pt->matrix[1][0] = pixman_double_to_fixed(wm->d[1]);
-			return;
+	pt->matrix[1][1] = pixman_double_to_fixed(wm->d[5]);
-
+	pt->matrix[1][2] = pixman_double_to_fixed(wm->d[13]);
-		src_x = 0.0;
+	pt->matrix[2][0] = pixman_double_to_fixed(wm->d[3]);
-		src_y = 0.0;
+	pt->matrix[2][1] = pixman_double_to_fixed(wm->d[7]);
-		src_width = surface->width_from_buffer;
+	pt->matrix[2][2] = pixman_double_to_fixed(wm->d[15]);
-		src_height = surface->height_from_buffer;
-	} else {
-		src_x = wl_fixed_to_double(vp->buffer.src_x);
-		src_y = wl_fixed_to_double(vp->buffer.src_y);
-		src_width = wl_fixed_to_double(vp->buffer.src_width);
-		src_height = wl_fixed_to_double(vp->buffer.src_height);
-	}
-
-	pixman_transform_scale(transform, NULL,
-			       D2F(src_width / surface->width),
-			       D2F(src_height / surface->height));
-	pixman_transform_translate(transform, NULL, D2F(src_x), D2F(src_y));
 }
 
 static void
@@ -181,7 +169,7 @@ repaint_region(struct weston_view *ev, struct weston_output *output,
 	pixman_region32_t final_region;
 	float view_x, view_y;
 	pixman_transform_t transform;
-	pixman_fixed_t fw, fh;
+	struct weston_matrix matrix;
 	pixman_image_t *mask_image;
 	pixman_color_t mask = { 0, };
 
@@ -218,121 +206,18 @@ repaint_region(struct weston_view *ev, struct weston_output *output,
 	/* Set up the source transformation based on the surface
 	   position, the output position/transform/scale and the client
 	   specified buffer transform/scale */
-	pixman_transform_init_identity(&transform);
+	weston_matrix_invert(&matrix, &output->matrix);
-	pixman_transform_scale(&transform, NULL,
-			       pixman_double_to_fixed ((double)1.0/output->current_scale),
-			       pixman_double_to_fixed ((double)1.0/output->current_scale));
-
-	fw = pixman_int_to_fixed(output->width);
-	fh = pixman_int_to_fixed(output->height);
-	switch (output->transform) {
-	default:
-	case WL_OUTPUT_TRANSFORM_NORMAL:
-	case WL_OUTPUT_TRANSFORM_FLIPPED:
-		break;
-	case WL_OUTPUT_TRANSFORM_90:
-	case WL_OUTPUT_TRANSFORM_FLIPPED_90:
-		pixman_transform_rotate(&transform, NULL, 0, -pixman_fixed_1);
-		pixman_transform_translate(&transform, NULL, 0, fh);
-		break;
-	case WL_OUTPUT_TRANSFORM_180:
-	case WL_OUTPUT_TRANSFORM_FLIPPED_180:
-		pixman_transform_rotate(&transform, NULL, -pixman_fixed_1, 0);
-		pixman_transform_translate(&transform, NULL, fw, fh);
-		break;
-	case WL_OUTPUT_TRANSFORM_270:
-	case WL_OUTPUT_TRANSFORM_FLIPPED_270:
-		pixman_transform_rotate(&transform, NULL, 0, pixman_fixed_1);
-		pixman_transform_translate(&transform, NULL, fw, 0);
-		break;
-	}
-
-	switch (output->transform) {
-	case WL_OUTPUT_TRANSFORM_FLIPPED:
-	case WL_OUTPUT_TRANSFORM_FLIPPED_90:
-	case WL_OUTPUT_TRANSFORM_FLIPPED_180:
-	case WL_OUTPUT_TRANSFORM_FLIPPED_270:
-		pixman_transform_scale(&transform, NULL,
-				       pixman_int_to_fixed (-1),
-				       pixman_int_to_fixed (1));
-		pixman_transform_translate(&transform, NULL, fw, 0);
-		break;
-	}
-
-        pixman_transform_translate(&transform, NULL,
-				   pixman_double_to_fixed (output->x),
-				   pixman_double_to_fixed (output->y));
 
 	if (ev->transform.enabled) {
-		/* Pixman supports only 2D transform matrix, but Weston uses 3D,
+		weston_matrix_multiply(&matrix, &ev->transform.inverse);
-		 * so we're omitting Z coordinate here
-		 */
-		pixman_transform_t surface_transform = {{
-				{ D2F(ev->transform.matrix.d[0]),
-				  D2F(ev->transform.matrix.d[4]),
-				  D2F(ev->transform.matrix.d[12]),
-				},
-				{ D2F(ev->transform.matrix.d[1]),
-				  D2F(ev->transform.matrix.d[5]),
-				  D2F(ev->transform.matrix.d[13]),
-				},
-				{ D2F(ev->transform.matrix.d[3]),
-				  D2F(ev->transform.matrix.d[7]),
-				  D2F(ev->transform.matrix.d[15]),
-				}
-			}};
-
-		pixman_transform_invert(&surface_transform, &surface_transform);
-		pixman_transform_multiply (&transform, &surface_transform, &transform);
 	} else {
-		pixman_transform_translate(&transform, NULL,
+		weston_matrix_translate(&matrix,
-					   pixman_double_to_fixed ((double)-ev->geometry.x),
+					-ev->geometry.x, -ev->geometry.y, 0);
-					   pixman_double_to_fixed ((double)-ev->geometry.y));
-	}
-
-	transform_apply_viewport(&transform, ev->surface);
-
-	fw = pixman_int_to_fixed(ev->surface->width_from_buffer);
-	fh = pixman_int_to_fixed(ev->surface->height_from_buffer);
-
-	switch (vp->buffer.transform) {
-	case WL_OUTPUT_TRANSFORM_FLIPPED:
-	case WL_OUTPUT_TRANSFORM_FLIPPED_90:
-	case WL_OUTPUT_TRANSFORM_FLIPPED_180:
-	case WL_OUTPUT_TRANSFORM_FLIPPED_270:
-		pixman_transform_scale(&transform, NULL,
-				       pixman_int_to_fixed (-1),
-				       pixman_int_to_fixed (1));
-		pixman_transform_translate(&transform, NULL, fw, 0);
-		break;
 	}
 
-	switch (vp->buffer.transform) {
+	weston_matrix_multiply(&matrix, &ev->surface->surface_to_buffer_matrix);
-	default:
-	case WL_OUTPUT_TRANSFORM_NORMAL:
-	case WL_OUTPUT_TRANSFORM_FLIPPED:
-		break;
-	case WL_OUTPUT_TRANSFORM_90:
-	case WL_OUTPUT_TRANSFORM_FLIPPED_90:
-		pixman_transform_rotate(&transform, NULL, 0, pixman_fixed_1);
-		pixman_transform_translate(&transform, NULL, fh, 0);
-		break;
-	case WL_OUTPUT_TRANSFORM_180:
-	case WL_OUTPUT_TRANSFORM_FLIPPED_180:
-		pixman_transform_rotate(&transform, NULL, -pixman_fixed_1, 0);
-		pixman_transform_translate(&transform, NULL, fw, fh);
-		break;
-	case WL_OUTPUT_TRANSFORM_270:
-	case WL_OUTPUT_TRANSFORM_FLIPPED_270:
-		pixman_transform_rotate(&transform, NULL, 0, -pixman_fixed_1);
-		pixman_transform_translate(&transform, NULL, 0, fw);
-		break;
-	}
-
-	pixman_transform_scale(&transform, NULL,
-			       pixman_double_to_fixed(vp->buffer.scale),
-			       pixman_double_to_fixed(vp->buffer.scale));
 
+	weston_matrix_to_pixman_transform(&transform, &matrix);
 	pixman_image_set_transform(ps->image, &transform);
 
 	if (ev->transform.enabled || output->current_scale != vp->buffer.scale)