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[Linux] Make glBlitFramebuffer optional in the OpenGL compositor - #189476
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robert-ancell merged 2 commits intoAug 19, 2026
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glBlitFramebuffer is a GLES3 / OpenGL 3.0 function and is not guaranteed to be present, so the Linux embedder should treat it as optional. The compositor was calling it unconditionally to blit the first layer, which breaks on OpenGL 2.0 drivers without the GL_EXT_framebuffer_blit extension and on drivers with a broken implementation (NVIDIA, Vivante, ARM per flutter#152099). Restore the blit-availability detection (GL version >= 3.0 or the GL_EXT_framebuffer_blit extension, plus the driver blacklist) and fall back to shader-based compositing for the first layer when blit is unavailable. This regressed in e983e59 ("Perform OpenGL compositing in the Flutter thread and write to a framebuffer." flutter#172090), which consolidated compositing and dropped the has_gl_framebuffer_blit check. Strengthen the NoBlitFramebuffer and BlitFramebufferNvidia tests to assert glBlitFramebuffer is never called. Fixes flutter#189322
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This pull request introduces a check to determine if the OpenGL driver supports glBlitFramebuffer (excluding certain vendors like Vivante, ARM, and NVIDIA) and falls back to shader-based compositing if unsupported or unavailable. Corresponding tests are updated to verify that glBlitFramebuffer is not called under these conditions. The reviewer suggests caching the result of can_blit_framebuffer() in the FlCompositorOpenGL instance to avoid the overhead of querying the driver vendor and performing string matching on every frame.
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Compute whether glBlitFramebuffer can be used once during fl_compositor_opengl_new and store the result in the compositor, instead of re-evaluating it on every frame in fl_compositor_opengl_composite_layers. Construct the compositor in each test after configuring the mocked OpenGL version/vendor/extensions so the cached value reflects the scenario under test.
This was referenced Aug 19, 2026
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glBlitFramebuffer is a GLES3 / OpenGL 3.0 function and is not guaranteed to be present, so the Linux embedder should treat it as optional. The compositor was calling it unconditionally to blit the first layer, which breaks on OpenGL 2.0 drivers without the GL_EXT_framebuffer_blit extension and on drivers with a broken implementation (NVIDIA, Vivante, ARM per #152099).
Restore the blit-availability detection (GL version >= 3.0 or the GL_EXT_framebuffer_blit extension, plus the driver blacklist) and fall back to shader-based compositing for the first layer when blit is unavailable.
This regressed in e983e59 ("Perform OpenGL compositing in the Flutter thread and write to a framebuffer." #172090), which consolidated compositing and dropped the has_gl_framebuffer_blit check.
Strengthen the NoBlitFramebuffer and BlitFramebufferNvidia tests to assert glBlitFramebuffer is never called.
Fixes #189322