Bug 1913568 - Add support for normalized UV coordinates to webrender. r=gfx-reviewers,nical

Some external images must be sampled from by providing normalized UV
coordinates to webrender, but currently webrender only supports
unnormalized UVs.

This patch adds a flag to webrender's external image API that
specifies whether the UV coordinates supplied when the texture is
locked are normalized or unnormalized. This flag is plumbed through
webrender to the required locations. We then add support for taking
normalized UVs as inputs to the brush_image and cs_scale shaders. The
only other shader that can be used with external textures is the
composite shader, which already supports normalized UVs.

This does not change any behaviour, that will happen in the next patch
in this series.

Differential Revision: https://phabricator.services.mozilla.com/D220581

Author: jamienicol

src/bindings.rs

@@ -2177,6 +2177,7 @@ pub extern "C" fn wr_resource_updates_add_external_image(
     external_image_id: ExternalImageId,
     image_type: &ExternalImageType,
     channel_index: u8,
+    normalized_uvs: bool,
 ) {
     txn.add_image(
         image_key,
@@ -2185,6 +2186,7 @@ pub extern "C" fn wr_resource_updates_add_external_image(
             id: external_image_id,
             channel_index,
             image_type: *image_type,
+            normalized_uvs,
         }),
         None,
     );
@@ -2222,6 +2224,7 @@ pub extern "C" fn wr_resource_updates_update_external_image(
     external_image_id: ExternalImageId,
     image_type: &ExternalImageType,
     channel_index: u8,
+    normalized_uvs: bool,
 ) {
     txn.update_image(
         key,
@@ -2230,6 +2233,7 @@ pub extern "C" fn wr_resource_updates_update_external_image(
             id: external_image_id,
             channel_index,
             image_type: *image_type,
+            normalized_uvs,
         }),
         &DirtyRect::All,
     );
@@ -2243,6 +2247,7 @@ pub extern "C" fn wr_resource_updates_update_external_image_with_dirty_rect(
     external_image_id: ExternalImageId,
     image_type: &ExternalImageType,
     channel_index: u8,
+    normalized_uvs: bool,
     dirty_rect: DeviceIntRect,
 ) {
     txn.update_image(
@@ -2252,6 +2257,7 @@ pub extern "C" fn wr_resource_updates_update_external_image_with_dirty_rect(
             id: external_image_id,
             channel_index,
             image_type: *image_type,
+            normalized_uvs,
         }),
         &DirtyRect::Partial(dirty_rect),
     );