compositor: gather buffer_transform and _scale into a struct

Gather the variables affecting the coordinate transformations between
buffer and local coordinates into a new struct weston_buffer_viewport.

This will be more useful later, when the crop & scale extension is
implemented.
diff --git a/src/compositor-drm.c b/src/compositor-drm.c
index a1d9d59..c34fc1c 100644
--- a/src/compositor-drm.c
+++ b/src/compositor-drm.c
@@ -463,7 +463,7 @@
 	    buffer == NULL || c->gbm == NULL ||
 	    buffer->width != output->base.current_mode->width ||
 	    buffer->height != output->base.current_mode->height ||
-	    output->base.transform != ev->surface->buffer_transform ||
+	    output->base.transform != ev->surface->buffer_viewport.transform ||
 	    ev->transform.enabled)
 		return NULL;
 
@@ -818,10 +818,10 @@
 	if (c->gbm == NULL)
 		return NULL;
 
-	if (ev->surface->buffer_transform != output_base->transform)
+	if (ev->surface->buffer_viewport.transform != output_base->transform)
 		return NULL;
 
-	if (ev->surface->buffer_scale != output_base->current_scale)
+	if (ev->surface->buffer_viewport.scale != output_base->current_scale)
 		return NULL;
 
 	if (c->sprites_are_broken)
@@ -931,8 +931,9 @@
 
 	tbox = weston_transformed_rect(wl_fixed_from_int(ev->geometry.width),
 				       wl_fixed_from_int(ev->geometry.height),
-				       ev->surface->buffer_transform,
-				       ev->surface->buffer_scale, tbox);
+				       ev->surface->buffer_viewport.transform,
+				       ev->surface->buffer_viewport.scale,
+				       tbox);
 
 	s->src_x = tbox.x1 << 8;
 	s->src_y = tbox.y1 << 8;
diff --git a/src/compositor.c b/src/compositor.c
index 4668c2a..59b4a53 100644
--- a/src/compositor.c
+++ b/src/compositor.c
@@ -399,10 +399,9 @@
 	surface->compositor = compositor;
 	surface->ref_count = 1;
 
-	surface->buffer_transform = WL_OUTPUT_TRANSFORM_NORMAL;
-	surface->buffer_scale = 1;
-	surface->pending.buffer_transform = surface->buffer_transform;
-	surface->pending.buffer_scale = surface->buffer_scale;
+	surface->buffer_viewport.transform = WL_OUTPUT_TRANSFORM_NORMAL;
+	surface->buffer_viewport.scale = 1;
+	surface->pending.buffer_viewport = surface->buffer_viewport;
 	surface->output = NULL;
 	surface->pending.newly_attached = 0;
 
@@ -638,8 +637,8 @@
 {
 	weston_transformed_coord(surface->width,
 				 surface->height,
-				 surface->buffer_transform,
-				 surface->buffer_scale,
+				 surface->buffer_viewport.transform,
+				 surface->buffer_viewport.scale,
 				 sx, sy, bx, by);
 }
 
@@ -651,8 +650,8 @@
 
 	weston_transformed_coord(surface->width,
 				 surface->height,
-				 surface->buffer_transform,
-				 surface->buffer_scale,
+				 surface->buffer_viewport.transform,
+				 surface->buffer_viewport.scale,
 				 sx, sy, &bxf, &byf);
 	*bx = floorf(bxf);
 	*by = floorf(byf);
@@ -664,8 +663,8 @@
 {
 	return weston_transformed_rect(surface->width,
 				       surface->height,
-				       surface->buffer_transform,
-				       surface->buffer_scale,
+				       surface->buffer_viewport.transform,
+				       surface->buffer_viewport.scale,
 				       rect);
 }
 
@@ -1145,7 +1144,7 @@
 weston_surface_buffer_width(struct weston_surface *surface)
 {
 	int32_t width;
-	switch (surface->buffer_transform) {
+	switch (surface->buffer_viewport.transform) {
 	case WL_OUTPUT_TRANSFORM_90:
 	case WL_OUTPUT_TRANSFORM_270:
 	case WL_OUTPUT_TRANSFORM_FLIPPED_90:
@@ -1156,14 +1155,14 @@
 		width = surface->buffer_ref.buffer->width;
                 break;
 	}
-	return width / surface->buffer_scale;
+	return width / surface->buffer_viewport.scale;
 }
 
 WL_EXPORT int32_t
 weston_surface_buffer_height(struct weston_surface *surface)
 {
 	int32_t height;
-	switch (surface->buffer_transform) {
+	switch (surface->buffer_viewport.transform) {
 	case WL_OUTPUT_TRANSFORM_90:
 	case WL_OUTPUT_TRANSFORM_270:
 	case WL_OUTPUT_TRANSFORM_FLIPPED_90:
@@ -1174,7 +1173,7 @@
 		height = surface->buffer_ref.buffer->height;
                 break;
 	}
-	return height / surface->buffer_scale;
+	return height / surface->buffer_viewport.scale;
 }
 
 WL_EXPORT uint32_t
@@ -1963,10 +1962,8 @@
 	pixman_region32_t opaque;
 
 	/* wl_surface.set_buffer_transform */
-	surface->buffer_transform = surface->pending.buffer_transform;
-
 	/* wl_surface.set_buffer_scale */
-	surface->buffer_scale = surface->pending.buffer_scale;
+	surface->buffer_viewport = surface->pending.buffer_viewport;
 
 	/* wl_surface.attach */
 	if (surface->pending.buffer || surface->pending.newly_attached)
@@ -2066,7 +2063,7 @@
 {
 	struct weston_surface *surface = wl_resource_get_user_data(resource);
 
-	surface->pending.buffer_transform = transform;
+	surface->pending.buffer_viewport.transform = transform;
 }
 
 static void
@@ -2076,7 +2073,7 @@
 {
 	struct weston_surface *surface = wl_resource_get_user_data(resource);
 
-	surface->pending.buffer_scale = scale;
+	surface->pending.buffer_viewport.scale = scale;
 }
 
 static const struct wl_surface_interface surface_interface = {
@@ -2197,10 +2194,8 @@
 	pixman_region32_t opaque;
 
 	/* wl_surface.set_buffer_transform */
-	surface->buffer_transform = sub->cached.buffer_transform;
-
 	/* wl_surface.set_buffer_scale */
-	surface->buffer_scale = sub->cached.buffer_scale;
+	surface->buffer_viewport = sub->cached.buffer_viewport;
 
 	/* wl_surface.attach */
 	if (sub->cached.buffer_ref.buffer || sub->cached.newly_attached)
@@ -2293,8 +2288,7 @@
 	surface->pending.sy = 0;
 	surface->pending.newly_attached = 0;
 
-	sub->cached.buffer_transform = surface->pending.buffer_transform;
-	sub->cached.buffer_scale = surface->pending.buffer_scale;
+	sub->cached.buffer_viewport = surface->pending.buffer_viewport;
 
 	pixman_region32_copy(&sub->cached.opaque, &surface->pending.opaque);
 
diff --git a/src/compositor.h b/src/compositor.h
index 8c19619..e445dc3 100644
--- a/src/compositor.h
+++ b/src/compositor.h
@@ -647,6 +647,14 @@
 	struct wl_listener destroy_listener;
 };
 
+struct weston_buffer_viewport {
+	/* wl_surface.set_buffer_transform */
+	uint32_t transform;
+
+	/* wl_surface.set_scaling_factor */
+	int32_t scale;
+};
+
 struct weston_region {
 	struct wl_resource *resource;
 	pixman_region32_t region;
@@ -693,10 +701,8 @@
 		struct wl_list frame_callback_list;
 
 		/* wl_surface.set_buffer_transform */
-		uint32_t buffer_transform;
-
 		/* wl_surface.set_buffer_scale */
-		int32_t buffer_scale;
+		struct weston_buffer_viewport buffer_viewport;
 	} cached;
 
 	int synchronized;
@@ -835,8 +841,7 @@
 	struct wl_list frame_callback_list;
 
 	struct weston_buffer_reference buffer_ref;
-	uint32_t buffer_transform;
-	int32_t buffer_scale;
+	struct weston_buffer_viewport buffer_viewport;
 	int keep_buffer; /* bool for backends to prevent early release */
 
 	/* All the pending state, that wl_surface.commit will apply. */
@@ -861,10 +866,8 @@
 		struct wl_list frame_callback_list;
 
 		/* wl_surface.set_buffer_transform */
-		uint32_t buffer_transform;
-
 		/* wl_surface.set_scaling_factor */
-		int32_t buffer_scale;
+		struct weston_buffer_viewport buffer_viewport;
 	} pending;
 
 	/*
diff --git a/src/gl-renderer.c b/src/gl-renderer.c
index 52451cd..a74aef5 100644
--- a/src/gl-renderer.c
+++ b/src/gl-renderer.c
@@ -536,7 +536,7 @@
 	shader_uniforms(gs->shader, ev, output);
 
 	if (ev->transform.enabled || output->zoom.active ||
-	    output->current_scale != ev->surface->buffer_scale)
+	    output->current_scale != ev->surface->buffer_viewport.scale)
 		filter = GL_LINEAR;
 	else
 		filter = GL_NEAREST;
diff --git a/src/pixman-renderer.c b/src/pixman-renderer.c
index b719829..5961965 100644
--- a/src/pixman-renderer.c
+++ b/src/pixman-renderer.c
@@ -260,7 +260,7 @@
 	fw = pixman_int_to_fixed(ev->geometry.width);
 	fh = pixman_int_to_fixed(ev->geometry.height);
 
-	switch (ev->surface->buffer_transform) {
+	switch (ev->surface->buffer_viewport.transform) {
 	case WL_OUTPUT_TRANSFORM_FLIPPED:
 	case WL_OUTPUT_TRANSFORM_FLIPPED_90:
 	case WL_OUTPUT_TRANSFORM_FLIPPED_180:
@@ -272,7 +272,7 @@
 		break;
 	}
 
-	switch (ev->surface->buffer_transform) {
+	switch (ev->surface->buffer_viewport.transform) {
 	default:
 	case WL_OUTPUT_TRANSFORM_NORMAL:
 	case WL_OUTPUT_TRANSFORM_FLIPPED:
@@ -295,12 +295,12 @@
 	}
 
 	pixman_transform_scale(&transform, NULL,
-			       pixman_double_to_fixed ((double)ev->surface->buffer_scale),
-			       pixman_double_to_fixed ((double)ev->surface->buffer_scale));
+			       pixman_double_to_fixed ((double)ev->surface->buffer_viewport.scale),
+			       pixman_double_to_fixed ((double)ev->surface->buffer_viewport.scale));
 
 	pixman_image_set_transform(ps->image, &transform);
 
-	if (ev->transform.enabled || output->current_scale != ev->surface->buffer_scale)
+	if (ev->transform.enabled || output->current_scale != ev->surface->buffer_viewport.scale)
 		pixman_image_set_filter(ps->image, PIXMAN_FILTER_BILINEAR, NULL, 0);
 	else
 		pixman_image_set_filter(ps->image, PIXMAN_FILTER_NEAREST, NULL, 0);
diff --git a/src/shell.c b/src/shell.c
index 2084ed6..605f090 100644
--- a/src/shell.c
+++ b/src/shell.c
@@ -2333,11 +2333,11 @@
 	case WL_SHELL_SURFACE_FULLSCREEN_METHOD_DRIVER:
 		if (shell_surface_is_top_fullscreen(shsurf)) {
 			struct weston_mode mode = {0,
-				surf_width * surface->buffer_scale,
-				surf_height * surface->buffer_scale,
+				surf_width * surface->buffer_viewport.scale,
+				surf_height * surface->buffer_viewport.scale,
 				shsurf->fullscreen.framerate};
 
-			if (weston_output_switch_mode(output, &mode, surface->buffer_scale,
+			if (weston_output_switch_mode(output, &mode, surface->buffer_viewport.scale,
 					WESTON_MODE_SWITCH_SET_TEMPORARY) == 0) {
 				weston_view_set_position(shsurf->view,
 							 output->x - surf_x,