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Tech Tip: The "Accelerated Screen Updates" setting
Published On: September 3, 1999

If you enable the "Accelerated Screen Updates" option, a portion of 4D's memory will be used as an offscreen bitmap area, enabling faster screen redraws and preventing screen blinking. The larger the resolution of your monitor and the higher its color bit depth setting, the more memory will be used for this offscreen bitmap. Its size can be as much as 3 MB or more.

The memory used to hold this offscreen bitmap is taken out of the same memory area used to hold copies of current records; structure objects such as forms, methods, and lists; process stacks, variables, arrays, sets, plug-in code, plug-in memory, and resources. Examples of the resources that can be loaded into this area of memory include network components, cursors, icons, menus, fonts, patterns, string resources, TRIC resources, and pictures such as the splash screen graphic. Using memory for an offscreen bitmap means that there will be less memory available to hold these other objects.

The "Accelerated Screen Updates" setting does not work well with the combination of video board and video driver in some computers. If you experience strange screen draw problems, try turning off this setting.

The "Accelerated Screen Updates" setting can be changed either in the "General" tab of the Database Properties dialog. After changing it here, you do not need to restart your application for the setting to be effective.

The setting can also be changed by using Customizer Plus to edit the "Screen Update" resource of the preference file for your 4D application.

The formula to calculate the amount of memory (in bytes) that the offscreen bitmap will use is:

(Screen width x screen height x (color bit depth/8)) + ((Screen height x screen width)/64)

For example, if your monitor resolution is 640 x 480 pixels, and your color bit depth is "256 colors," then 305K of memory will be needed for the offscreen bitmap.

If your monitor resolution is 1,024 x 768 pixels, and your color bit depth is "millions of colors," then 3,084K (over 3 MB) of memory will be needed for the offscreen bitmap.

The only place where this setting is stored is in the "Screen Update" resource of the preference files. On Windows, these files are named "4DV6Prf.RSR", "EngV6Prf.RSR", and "RunV6Prf.RSR". On Macintosh, these files are named "4DV6Prf", "EngV6Prf", and "RunV6Prf".

The preferences files do not by default contain the "Screen Update" resource (the resource is disabled). This resource is created if you change the Accelerated Screen Updates setting, whether you change the setting directly by using Customizer Plus, or if you change the setting in the Database Properties dialog. If there is no preferences file, or if the "Screen Update" resource does not exist in the preferences file, then the setting defaults to being turned off.

Note: The "4DV6Prf.RSR" file also stores your 4D v6 and 4D Server v6 licensing information, including expansion pack licenses, so don't casually delete it. (4D v6.5 and 4D Server v6.5 store their licensing and expansion pack information in the Windows Registry. The "4DV6Prf.RSR" file also stores the list of the paths to the databases most recently used with 4D v6.5.) The "RunV6Prf.RSR" file (used by 4D Runtime and 4D Runtime Classic) and the "EngV6Prf.RSR" file (used by structures compiled and merged with 4D Engine) do not store licensing information.