Window Regions And Coordinates; Figure 11.1: Window Regions - Texas Instruments TI-89 Developer's Manual

Chapter 11: Creating the User Interface
windows. When an application is started (gets the CM_START message), it gets
a WIN_RECT that defines the region of its window. This region is based on
whether the calculator is in full or split screen mode and the side of the screen
split of the current app. An app can create additional windows which may
overlap.
11.2.1.

Window Regions and Coordinates

A window region is limited to a rectangular area defined by two coordinate pairs:
an x, y pair that defines the upper left corner of the region and an x, y pair that
defines the lower right corner of the region. All window region coordinates are
represented as signed 16-bit numbers. The coordinate (0, 0) is the upper left
corner of a region. Since coordinates may be negative, the coordinate (L1, L1) is
up one pixel and over one pixel to the left of the coordinate (0, 0).
A window has three regions associated with it. The first region, the actual
window, is the region that was defined when the window was created. The
second region is the area of that window that may be drawn to, the client region.
If the window is full screen (not counting the application's menu or the status bar
which may not be overlapped), then the client region is equal to the window
region. The client region is reduced by adding borders or a title to a window.
Each window also has a clipping region which is a subset of the client region.
Initially, the clipping region is equal to the client region but it may be changed by
the app with the SetWinClip routine. The following graphic illustrates the three
window regions.
Real windows are limited to the size of the screen. Virtual windows are allocated
a bitmap in memory and are limited to unsigned coordinates of the region
(0, 0) . . . (255, 255). The size of the virtual window must not exceed the
maximum allowable block of heap memory.
TI-89 / TI-92 Plus Developer Guide

Figure 11.1: Window Regions

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Beta Version January 26, 2001