Route paint UI clear state through GL backend

src/renderer_gl/opengl_capabilities.cpp

@@ -481,6 +481,18 @@ pp::foundation::Status clear_opengl_render_target(
     return pp::foundation::Status::success();
 }
 
+pp::foundation::Status apply_opengl_clear_color(
+    std::array<float, 4> color,
+    OpenGlClearColorDispatch dispatch) noexcept
+{
+    if (dispatch.clear_color == nullptr) {
+        return pp::foundation::Status::invalid_argument("OpenGL clear-color dispatch callback must not be null");
+    }
+
+    dispatch.clear_color(color[0], color[1], color[2], color[3]);
+    return pp::foundation::Status::success();
+}
+
 pp::foundation::Status clear_opengl_color_buffer_with_write_mask(
     OpenGlColorMaskedClear clear,
     OpenGlColorMaskedClearDispatch dispatch) noexcept
@@ -539,6 +551,37 @@ pp::foundation::Status apply_opengl_viewport(
     return pp::foundation::Status::success();
 }
 
+pp::foundation::Result<OpenGlViewportRect> query_opengl_viewport(
+    OpenGlViewportQueryDispatch dispatch) noexcept
+{
+    if (dispatch.get_integer == nullptr) {
+        return pp::foundation::Result<OpenGlViewportRect>::failure(
+            pp::foundation::Status::invalid_argument("OpenGL viewport query dispatch callback must not be null"));
+    }
+
+    std::array<std::int32_t, 4> viewport {};
+    dispatch.get_integer(viewport_query(), viewport.data());
+    return pp::foundation::Result<OpenGlViewportRect>::success(OpenGlViewportRect {
+        .x = viewport[0],
+        .y = viewport[1],
+        .width = viewport[2],
+        .height = viewport[3],
+    });
+}
+
+pp::foundation::Result<std::array<float, 4>> query_opengl_clear_color(
+    OpenGlClearColorQueryDispatch dispatch) noexcept
+{
+    if (dispatch.get_float == nullptr) {
+        return pp::foundation::Result<std::array<float, 4>>::failure(
+            pp::foundation::Status::invalid_argument("OpenGL clear-color query dispatch callback must not be null"));
+    }
+
+    std::array<float, 4> color {};
+    dispatch.get_float(color_clear_value_query(), color.data());
+    return pp::foundation::Result<std::array<float, 4>>::success(color);
+}
+
 pp::foundation::Status apply_opengl_scissor_rect(
     OpenGlScissorRect scissor,
     OpenGlScissorDispatch dispatch) noexcept