[core] test OffscreenTexture renderability before using them

src/mbgl/gfx/offscreen_texture.hpp

@@ -17,6 +17,8 @@ protected:
 public:
     virtual ~OffscreenTexture() = default;
 
+    virtual bool isRenderable() = 0;
+
     virtual PremultipliedImage readStillImage() = 0;
     virtual gfx::Texture& getTexture() = 0;
 };

src/mbgl/gl/offscreen_texture.cpp

@@ -75,6 +75,15 @@ OffscreenTexture::OffscreenTexture(
           size, std::make_unique<OffscreenTextureResource>(context, size_, renderbuffer, type)) {
 }
 
+bool OffscreenTexture::isRenderable() {
+    try {
+        getResource<OffscreenTextureResource>().bind();
+        return true;
+    } catch (const std::runtime_error& ex) {
+        return false;
+    }
+}
+
 PremultipliedImage OffscreenTexture::readStillImage() {
     return getResource<OffscreenTextureResource>().readStillImage();
 }

src/mbgl/gl/offscreen_texture.hpp

@@ -18,6 +18,8 @@ public:
                      gfx::Renderbuffer<gfx::RenderbufferPixelType::Depth>&,
                      gfx::TextureChannelDataType type = gfx::TextureChannelDataType::UnsignedByte);
 
+    bool isRenderable() override;
+
     PremultipliedImage readStillImage() override;
     gfx::Texture& getTexture() override;
 };

src/mbgl/renderer/layers/render_heatmap_layer.cpp

@@ -62,10 +62,7 @@ void RenderHeatmapLayer::render(PaintParameters& parameters, RenderSource*) {
             if (parameters.context.supportsHalfFloatTextures) {
                 renderTexture = parameters.context.createOffscreenTexture(size, gfx::TextureChannelDataType::HalfFloat);
 
-                // TODO: try binding in the offscreen texture constructor
-                try {
-                    renderTexture->getResource<gl::RenderableResource>().bind();
-                } catch (const std::runtime_error& ex) {
+                if (!renderTexture->isRenderable()) {
                     // can't render to a half-float texture; falling back to unsigned byte one
                     renderTexture.reset();
                     parameters.context.supportsHalfFloatTextures = false;