Rendering changed portions of composited images

A non-transitory computer program product comprising one or more computer readable physical storage media having stored thereon computer executable instructions that when executed by a processor cause a computing system to perform a method for rendering an image on a display of a device, the method comprising:

• accessing a first frame, of an image to be rendered to the display of the device, in a first buffer;
• determining that one or more portions of the first frame will be unchanged in a second frame of the image and that one or more portions of the first frame will change in the second frame;
• copying the unchanged portions of the first frame to a second buffer;
• creating a list of instructions that when executed will generate the changed portions of the second frame;
• determining that at least one of the instructions in the list of instructions is at least partially redundant to at least one other instruction in the list of instructions;
• prior to executing the list of instructions, optimizing the list of instructions by removing at least one instruction that is at least partially redundant;
• and
• executing the optimized list of instructions to generate the changed portions of the second frame.

A portable electronic device comprising:

• a display able to present images to a user;
• a user interface through which the user provides input;
• and
• a graphic engine that renders images painted on the display of the device, the graphic engine including;
• a plurality of buffers that are used in round robin fashion to generate successive frames painted in the display;
• and
• an image module that manages the plurality of buffers and repairs portions of the image that are damaged by performing the following:
• accessing a first frame, of an image to be rendered to the display of the device, in a first buffer;
• determining that one or more portions of the first frame will be unchanged in a second frame of the image and that one or more portions of the first frame will change in the second frame;
• copying the unchanged portions of the first frame to a second buffer;
• creating a list of instructions that when executed will generate the changed portions of the second frame;
• determining that at least one of the instructions in the list of instructions is at least partially redundant to at least one other instruction in the list of instructions;
• prior to executing the list of instructions, optimizing the list of instructions by removing at least one instruction that is at least partially redundant;
• and
• executing the optimized list of instructions to generate the changed portions of the second frame.