Auto merge of #3338 - jamienicol:copyimagesubdata, r=kvark

Use glCopyImageSubData where available to copy data between texture arrays

Falling back to the existing glBlitFramebuffer loop. This avoids a
driver bug with texture arrays and glBlitFramebuffer on Adreno 4xx,
5xx, and 6xx devices, where the blit was failing and the texture cache
became corrupted.

Adreno 3xx seems to be affected by a similar bug, but does not support
glCopyImageSubData, so this can not be used there. Once the exact
nature of that bug has been established and a workaround identified,
we should re-evaluate whether this change is still desirable or if the
code paths can be consolidated.

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Author: bors-servo

Cargo.lock

@@ -8,12 +8,15 @@ check-alphabetical-order = false
 packages = [
     "crossbeam-epoch",
     "crossbeam-utils",
+    "gl_generator",
+    "khronos_api",
     "lazy_static",
     "log",
     "rand",
     "winapi",
     "core-graphics",
     "core-text",
+    "xml-rs",
     "yaml-rust",
 ]
 

servo-tidy.toml

@@ -26,7 +26,7 @@ bitflags = "1.0"
 byteorder = "1.0"
 cfg-if = "0.1.2"
 fxhash = "0.2.1"
-gleam = "0.6.3"
+gleam = "0.6.8"
 image = { optional = true, version = "0.20" }
 lazy_static = "1"
 log = "0.4"

webrender/Cargo.toml

@@ -857,6 +857,9 @@ pub struct Device {
     /// format, we fall back to glTexImage*.
     texture_storage_usage: TexStorageUsage,
 
+    /// Whether the function glCopyImageSubData is available.
+    supports_copy_image_sub_data: bool,
+
     // GL extensions
     extensions: Vec<String>,
 }
@@ -1024,6 +1027,9 @@ impl Device {
             )
         };
 
+        let supports_copy_image_sub_data = supports_extension(&extensions, "GL_EXT_copy_image") ||
+            supports_extension(&extensions, "GL_ARB_copy_image");
+
         // Explicitly set some global states to the values we expect.
         gl.disable(gl::FRAMEBUFFER_SRGB);
         gl.disable(gl::MULTISAMPLE);
@@ -1066,6 +1072,7 @@ impl Device {
             frame_id: GpuFrameId(0),
             extensions,
             texture_storage_usage,
+            supports_copy_image_sub_data
         }
     }
 
@@ -1621,15 +1628,27 @@ impl Device {
         debug_assert!(dst.size.height >= src.size.height);
         debug_assert!(dst.layer_count >= src.layer_count);
 
-        // Note that zip() truncates to the shorter of the two iterators.
-        let rect = DeviceIntRect::new(DeviceIntPoint::zero(), src.get_dimensions().to_i32());
-        for (read_fbo, draw_fbo) in src.fbos.iter().zip(&dst.fbos) {
-            self.bind_read_target_impl(*read_fbo);
-            self.bind_draw_target_impl(*draw_fbo);
-            self.blit_render_target(rect, rect);
+        if self.supports_copy_image_sub_data {
+            assert_ne!(src.id, dst.id,
+                    "glCopyImageSubData's behaviour is undefined if src and dst images are identical and the rectangles overlap.");
+            unsafe {
+                self.gl.copy_image_sub_data(src.id, src.target, 0,
+                                            0, 0, 0,
+                                            dst.id, dst.target, 0,
+                                            0, 0, 0,
+                                            src.size.width as _, src.size.height as _, src.layer_count);
+            }
+        } else {
+            // Note that zip() truncates to the shorter of the two iterators.
+            let rect = DeviceIntRect::new(DeviceIntPoint::zero(), src.get_dimensions().to_i32());
+            for (read_fbo, draw_fbo) in src.fbos.iter().zip(&dst.fbos) {
+                self.bind_read_target_impl(*read_fbo);
+                self.bind_draw_target_impl(*draw_fbo);
+                self.blit_render_target(rect, rect);
+            }
+            self.reset_draw_target();
+            self.reset_read_target();
         }
-        self.reset_draw_target();
-        self.reset_read_target();
     }
 
     /// Notifies the device that the contents of a render target are no longer