Display device interface including support for generalized flipping of surfaces

In a computer having a display controller for converting a pixmap into a display image on a display screen, a computer implemented method for controlling flipping comprising:

• in response to a request to flip a front buffer and a back buffer, evaluating whether to instruct the display controller to flip the front and back buffer including:
• determining whether a refresh period of the display controller has elapsed since a previous flip request;
• and
• reading a current position of the scan line and determining whether the current position of the scan line is less than a position of the scan line at the time of the previous flip request;
• if, based on the evaluating step, the display controller has completed a flip since the last flip request, then instructing the display controller to flip the front and back buffer.

A computer readable medium on which is stored an application programming interface (API) for controlling acces to a display controller, said API comprising instructions, which when executed by the computer, perform the steps of:

• in response to an API request to create a flippable surface, allocating front and back buffers in video or main memory, creating a flipping structure representing the front and back buffers, storing memory locations of the front and back buffers in the flipping structure, and storing surface type in the flipping structure, wherein the flipping structure represents an offscreen pixmap, a texture map, an overlay, a sprite, an alpha buffer, or a Z buffer;
• in response to an API request to lock a region of the front buffer or back buffer, determining whether an application or the display controller is currently accessing the region, and if not, giving a requesting application exclusive access to the region as long as the requesting application holds a lock for the region;
• and
• in response to an API request to flip the flippable surface, performing the steps of:
• determining whether any application or the display controller is accessing the front or back buffers, and
• when no application is accessing the front or back buffer and the display controller is not accessing the front or back buffer, flipping the front and back buffers and updating the memory locations of the front and back buffers stored in the flipping structure to reflect new memory locations of the front and back buffers.

A display device application programming interface implemented in a computer system including a processor, system memory, a display controller, and video memory, the display device API comprising:

• an interface function operable to create an instance of a display object in response to a create display object call from an application executing in the computer system,
• the display object including a create surface member function operable to create an instance of a flippable surface object representing a flippable surface of a type selected from the group consisting of:
• an offscreen pixmap,
• a texture map,
• an overlay,
• an alpha buffer, and
• a Z buffer;
• wherein each instance of the flippable surface object includes reference pointers to locations in video or system memory where corresponding flippable surfaces are stored, and includes data identifying the type of the flippable surface;
• and
• wherein the surface object includes a flip member function operable to control flipping of each instance of the flippable surface object, and lock and unlock member functions operable to synchronize access of one or more applications to the locations in video or system memory where the corresponding flippable surfaces are stored.

In a display device interface for a display controller that converts a primary surface into a display screen on a display monitor, a computer-implemented method for supporting generalized flipping of surface memory, the method comprising:

• in response to a request to create a primary flipping surface, creating a primary flipping surface structure;
• in the primary surface structure, storing a front buffer reference to a front buffer that holds a pixmap being displayed on the display screen, and storing a back buffer reference to a back buffer that holds pixmap to be displayed on the display screen;
• in response to a request to create a second flipping surface, creating a second flipping structure;
• in the second flipping surface structure, storing a front buffer reference to a front buffer for storing a first array of pixel data, and storing a back buffer reference to a back buffer for constructing a second array of pixel data, wherein the first and second arrays of pixel data are of a type selected from the group consisting of:
• an offscreen pixmap,
• a sprite,
• a texture map,
• an overlay,
• an alpha buffer, and
• a Z buffer;
• in response to a request to flip the primary flipping structure by an application, determining whether another application is currently accessing the front or back buffers corresponding to the primary flipping structure, determining whether the display controller has completed a previous flip request, and if no other application is accessing the front or back buffers and the display controller has completed a previous flip request, then writing an address of the back buffer to the display controller, and updating the front and back buffer references in the primary flipping structure;
• in response to a request to flip the second flipping structure from an application, determining whether another application is currently accessing the front or back buffers corresponding to the second flipping structure, and if not, updating the front and back buffer references in the second flipping structure;
• in response to requests from applications to access the front or back buffer of the primary flipping structure, synchronizing access to the back buffer of the primary flipping structure;
• and
• in response to requests from applications to access the front or back buffer of the second flipping structure, synchronizing access to the front buffer and back buffer of the second flipping structure.

In a display device interface for a display device controller that converts a primary surface into a display screen on a display monitor, a computer-implemented method for supporting generalized flipping of surface memory, the method comprising:

• receiving a call from an application to create a flipping structure, wherein the application designates any of the types of surfaces selected from the group consisting of:
• an offscreen pixmap,
• a pixmap that covers less than the entire display screen, a texture map,
• an overlay,
• an alpha buffer, and
• a Z buffer;
• in response to the call to create the flipping structure, creating a flipping structure including a front buffer for storing a first array of pixel data for use by a client other than the display device, and a back buffer for constructing a second array of pixel data;
• synchronizing access to the back buffer;
• and
• in response to a request to flip the flipping structure from an application, flipping the front and back buffer.