In a graphics processor, a rendering object and a post-processing object share access to a host processor with a programmable execution core. The rendering object generates fragment data for an image from geometry data. The post-processing object operates to generate a frame of pixel data from the fragment data and to store the pixel data in a frame buffer. In parallel with operations of the host processor, a scanout engine reads pixel data for a previously generated frame and supplies the pixel data to a display device. The scanout engine periodically triggers the host processor to operate the post-processing object to generate the next frame. Timing between the scanout engine and the post-processing object can be controlled such that the next frame to be displayed is ready in a frame buffer when the scanout engine finishes reading a current frame.