hal/gles: small fixes for external context

wgpu-hal/src/gles/adapter.rs

@@ -442,7 +442,8 @@ impl super::Adapter {
         let r = renderer.to_lowercase();
         // Check for Mesa sRGB clear bug. See
         // [`super::PrivateCapabilities::MESA_I915_SRGB_SHADER_CLEAR`].
-        if r.contains("mesa")
+        if context.is_owned()
+            && r.contains("mesa")
             && r.contains("intel")
             && r.split(&[' ', '(', ')'][..])
                 .any(|substr| substr.len() == 3 && substr.chars().nth(2) == Some('l'))

wgpu-hal/src/gles/egl.rs

@@ -293,6 +293,10 @@ unsafe impl Sync for AdapterContext {}
 unsafe impl Send for AdapterContext {}
 
 impl AdapterContext {
+    pub fn is_owned(&self) -> bool {
+        self.egl.is_some()
+    }
+
     #[cfg(feature = "renderdoc")]
     pub fn raw_context(&self) -> *mut raw::c_void {
         match self.egl {

wgpu-hal/src/gles/queue.rs

@@ -46,11 +46,13 @@ impl super::Queue {
         gl.draw_buffers(&[glow::COLOR_ATTACHMENT0 + draw_buffer]);
         gl.draw_arrays(glow::TRIANGLES, 0, 3);
 
-        // Reset the draw buffers to what they were before the clear
-        let indices = (0..self.draw_buffer_count as u32)
-            .map(|i| glow::COLOR_ATTACHMENT0 + i)
-            .collect::<ArrayVec<_, { crate::MAX_COLOR_TARGETS }>>();
-        gl.draw_buffers(&indices);
+        if self.draw_buffer_count != 0 {
+            // Reset the draw buffers to what they were before the clear
+            let indices = (0..self.draw_buffer_count as u32)
+                .map(|i| glow::COLOR_ATTACHMENT0 + i)
+                .collect::<ArrayVec<_, { crate::MAX_COLOR_TARGETS }>>();
+            gl.draw_buffers(&indices);
+        }
         #[cfg(not(target_arch = "wasm32"))]
         for draw_buffer in 0..self.draw_buffer_count as u32 {
             gl.disable_draw_buffer(glow::BLEND, draw_buffer);

wgpu-hal/src/gles/web.rs

@@ -11,6 +11,10 @@ pub struct AdapterContext {
 }
 
 impl AdapterContext {
+    pub fn is_owned(&self) -> bool {
+        false
+    }
+
     /// Obtain a lock to the EGL context and get handle to the [`glow::Context`] that can be used to
     /// do rendering.
     #[track_caller]