Make ImageDescriptor nicer to use.

sample/src/main.rs

@@ -105,14 +105,7 @@ fn main() {
     let vector_img = api.generate_image_key();
     api.add_image(
         vector_img,
-        ImageDescriptor {
-            format: ImageFormat::RGBA8,
-            width: 100,
-            height: 100,
-            stride: None,
-            is_opaque: true,
-            offset: 0,
-        },
+        ImageDescriptor::new(100, 100, ImageFormat::RGBA8).with_opaque_flag(true),
         ImageData::new_blob_image(Vec::new()),
     );
 
@@ -149,14 +142,7 @@ fn main() {
         let mask_image = api.generate_image_key();
         api.add_image(
             mask_image,
-            ImageDescriptor {
-                width: 2,
-                height: 2,
-                stride: None,
-                format: ImageFormat::A8,
-                is_opaque: true,
-                offset: 0,
-            },
+            ImageDescriptor::new(2, 2, ImageFormat::A8).with_opaque_flag(true),
             ImageData::new(vec![0, 80, 180, 255])
         );
         let mask = webrender_traits::ImageMask {

webrender/src/renderer.rs

@@ -698,27 +698,13 @@ impl Renderer {
         // TODO: Ensure that the white texture can never get evicted when the cache supports LRU eviction!
         let white_image_id = texture_cache.new_item_id();
         texture_cache.insert(white_image_id,
-                             ImageDescriptor {
-                                width: 2,
-                                height: 2,
-                                stride: None,
-                                offset: 0,
-                                format: ImageFormat::RGBA8,
-                                is_opaque: false,
-                             },
+                             ImageDescriptor::new(2, 2, ImageFormat::RGBA8),
                              TextureFilter::Linear,
                              ImageData::Raw(Arc::new(white_pixels)));
 
         let dummy_mask_image_id = texture_cache.new_item_id();
         texture_cache.insert(dummy_mask_image_id,
-                             ImageDescriptor {
-                                width: 2,
-                                height: 2,
-                                stride: None,
-                                offset: 0,
-                                format: ImageFormat::A8,
-                                is_opaque: false,
-                             },
+                             ImageDescriptor::new(2, 2, ImageFormat::A8),
                              TextureFilter::Linear,
                              ImageData::Raw(Arc::new(mask_pixels)));
 

webrender_traits/src/types.rs

@@ -368,6 +368,27 @@ pub struct ImageDescriptor {
 }
 
 impl ImageDescriptor {
+    pub fn new(width: u32, height: u32, format: ImageFormat) -> Self {
+        ImageDescriptor {
+            width: width,
+            height: height,
+            format: format,
+            stride: None,
+            offset: 0,
+            is_opaque: format == ImageFormat::RGB8,
+        }
+    }
+
+    pub fn with_opaque_flag(mut self, is_opaque: bool) -> Self {
+        self.is_opaque = is_opaque;
+        return self;
+    }
+
+    pub fn with_stride(mut self, stride: u32) -> Self {
+        self.stride = Some(stride);
+        return self;
+    }
+
     pub fn compute_stride(&self) -> u32 {
         self.stride.unwrap_or(self.width * self.format.bytes_per_pixel().unwrap())
     }