This snippet shows how to write a device loop that works under System 7 and pre-7.0 systems. As described on pages 21-23 and 21-24 of Inside Mac volume VI, a device loop procedure searches all active screen devices, calling a drawing procedure whenever it encounters a screen that intersects the drawing region. In this app the drawing region is the app's window bounds and the chosen drawing procedure simply displays the screen's colors for every device the window bounds intersect.
Building the Code
This project was built and tested on CodeWarrior 2.1 using CarbonLib 1.1a3. Since this is a Carbon app, the "Carbon Support" folder of the CarbonSDK should be in the same folder as the CodeWarrior IDE. If this is not the case, the CarbonLib library will have to be re-added to the project. In addition, the CarbonLib extension needs to be in the extension folder. The CarbonSDK (which contains the library and the extension) can be found on Apple's website: http://developer.apple.com/sdk/
Restrictions
Nearly every sample requires more memory than the 384KB CodeWarrior sets as the default heap size. If for some reason the memory has been reset to the default (either through converting the project or whatever) the memory should be reset to 1000 - 2000KB (depending on the application). This can be achieved by going to the projects settings (Edit Menu->C-PPC Settings... under CodeWarrior 2.1) and selecting the "PPC Target" under the "Target" tab.
Other Code Notes
This sample used to be a "non-Carbon" sample, but has been carbonized for demonstration purposes. The "old" code has been left in (commented out) in order to compare and contrast the Carbon versus non-Carbon APIs.
