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205 lines
7.8 KiB
Markdown
205 lines
7.8 KiB
Markdown
# Track Bar Control
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- [Styles of Track Bar](#styles-of-track-bar)
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- [Messages of Track Bar](#messages-of-track-bar)
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- [Notification Codes of Track Bar](#notification-codes-of-track-bar)
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- [Sample Program](#sample-program)
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The track bar is generally used for adjusting brightness, volume, etc. In the
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situation for adjusting the value in a range, track bar can be used. Calling
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`CreateWindow` function with `CTRL_TRACKBAR` as the control class name can
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create a track bar. Figure 1 shows the typical running effect of a track bar.
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__Figure 1__ Track bar control
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## Styles of Track Bar
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The frequently used combination of styles for a track bar is:
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```cpp
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WS_CHILD | WS_VISIBLE | TBS_NOTIFY
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```
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Specifying `TBS_NOTIFY` style can make a track bar generating notification
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messages.
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A track bar is horizontal by default. To create a vertical track bar, you can
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specify `TBS_VERTICAL` style. The track bar in Figure 2 is a vertical track
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bar.
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__Figure 2__ A vertical track bar
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Other styles of track bar are illustrated as follow:
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- `TBS_TIP`: Display the tip string beside the track bar (as “Min” and “Max” in
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Figure 1). A track bar with this style will also display the current position
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value in the center of the control.
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- `TBS_NOTICK`: Do not display the tick lines.
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- `TBS_BORDER`: This style makes a track bar having bordered, which is not used
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frequently.
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## Messages of Track Bar
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Messages of a track bar are relatively simple, as summarized in the following:
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- `TBM_SETRANGE`: Set the minimum and maximum positions for the track bar
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through `wParam` and `lParam` parameters. The default range is 0~10.
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- `TBM_GETMIN`: Get the minimum position for the track bar.
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- `TBM_GETMAX`: Get the maximum position for the track bar.
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- `TBM_SETMIN`: Set the minimum position for the track bar.
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- `TBM_SETMAX`: Set the maximum position for the track bar.
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- `TBM_SETLINESIZE`: Sets the step value by `wParam` parameter. When the user
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presses up or down arrow key during the track bar has input focus, the slider
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will be moved up or down the step value. The default step value is 1.
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- `TBM_GETLINESIZE`: Gets the step value of the slider.
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- `TBM_SETPAGESIZE`: Set the page step value by `wParam` parameter. When the
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user presses `PageUp` or `PageDown` key during the track bar has input focus,
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the slider will be moved up or down the page step value. The default page step
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value is 1.
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- `TBM_GETPAGESIZE`: Get the page step value of the track bar.
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- `TBM_SETPOS`: Set the position of the slider.
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- `TBM_GETPOS`: Get the position of the slider.
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- `TBM_SETTICKFREQ`: Set the interval value of tick marks in a track bar, the
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default interval is 1.
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- `TBM_GETTICKFREQ`: Get the interval value of tick marks in a track bar.
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- `TBM_SETTIP`: Set the tip string at the minimum and maximum positions.
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- `TBM_GETTIP`: Set the tip strings at the minimum and maximum positions.
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## Notification Codes of Track Bar
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The track bar with `TBS_NOTIFY` style may generate the following notification
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codes:
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- `TBN_CHANGE`: The position of the slider has changed.
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- `TBN_REACHMAX`: The slider has reached the maximum position.
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- `TBN_REACHMIN`: The slider has reached the minimum position.
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## Sample Program
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List 1 gives an example program of track bar. The program draws a circle with
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the corresponding size according to the current slider position. When the user
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changes the position of the slider, the circle will also be refreshed. The
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running effect of the program is shown in Figure 3. Please refer to `trackbar.c`
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file of the demo program package `mg-samples` of this guide for the complete
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source code.
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__List 1__ Use of track bar
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```cpp
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <minigui/common.h>
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#include <minigui/minigui.h>
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#include <minigui/gdi.h>
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#include <minigui/window.h>
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#include <minigui/control.h>
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static int radius = 10;
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static RECT rcCircle = {0, 60, 300, 300};
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static void my_notif_proc (HWND hwnd, int id, int nc, DWORD add_data)
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{
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if (nc == TBN_CHANGE) {
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/* When the position of the slider has changed,
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* save the current position, and inform the main window to redraw */
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radius = SendMessage (hwnd, TBM_GETPOS, 0, 0);
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InvalidateRect (GetParent (hwnd), &rcCircle, TRUE);
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}
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}
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static int TrackBarWinProc(HWND hWnd, int message, WPARAM wParam, LPARAM lParam)
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{
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HWND hwnd;
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switch (message) {
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case MSG_CREATE:
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/* Create a track bar */
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hwnd = CreateWindow (CTRL_TRACKBAR,
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"",
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WS_VISIBLE | TBS_NOTIFY,
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100,
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10, 10, 280, 50, hWnd, 0);
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/* Set the range, step vaue, interval value and current position */
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SendMessage (hwnd, TBM_SETRANGE, 0, 100);
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SendMessage (hwnd, TBM_SETLINESIZE, 1, 0);
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SendMessage (hwnd, TBM_SETPAGESIZE, 10, 0);
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SendMessage (hwnd, TBM_SETTICKFREQ, 10, 0);
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SendMessage (hwnd, TBM_SETPOS, radius, 0);
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/* Set the notification callback function of the slider */
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SetNotificationCallback (hwnd, my_notif_proc);
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break;
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case MSG_PAINT:
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{
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HDC hdc = BeginPaint (hWnd);
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/* Draw a circle with radius of the the current position of the slider */
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ClipRectIntersect (hdc, &rcCircle);
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Circle (hdc, 140, 120, radius);
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EndPaint (hWnd, hdc);
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return 0;
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}
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case MSG_DESTROY:
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DestroyAllControls (hWnd);
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return 0;
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case MSG_CLOSE:
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DestroyMainWindow (hWnd);
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PostQuitMessage (hWnd);
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return 0;
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}
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return DefaultMainWinProc(hWnd, message, wParam, lParam);
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}
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/* Following codes to create the main window are omitted */
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```
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__Figure 3__ Use of track bar
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----
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[<< Progress Bar Control](MiniGUIProgGuidePart6Chapter07.md) |
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[Table of Contents](README.md) |
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[Toolbar Control >>](MiniGUIProgGuidePart6Chapter09.md)
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[Release Notes for MiniGUI 3.2]: /supplementary-docs/Release-Notes-for-MiniGUI-3.2.md
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[Release Notes for MiniGUI 4.0]: /supplementary-docs/Release-Notes-for-MiniGUI-4.0.md
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[Showing Text in Complex or Mixed Scripts]: /supplementary-docs/Showing-Text-in-Complex-or-Mixed-Scripts.md
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[Supporting and Using Extra Input Messages]: /supplementary-docs/Supporting-and-Using-Extra-Input-Messages.md
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[Using CommLCD NEWGAL Engine and Comm IAL Engine]: /supplementary-docs/Using-CommLCD-NEWGAL-Engine-and-Comm-IAL-Engine.md
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[Using Enhanced Font Interfaces]: /supplementary-docs/Using-Enhanced-Font-Interfaces.md
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[Using Images and Fonts on System without File System]: /supplementary-docs/Using-Images-and-Fonts-on-System-without-File-System.md
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[Using SyncUpdateDC to Reduce Screen Flicker]: /supplementary-docs/Using-SyncUpdateDC-to-Reduce-Screen-Flicker.md
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[Writing DRI Engine Driver for Your GPU]: /supplementary-docs/Writing-DRI-Engine-Driver-for-Your-GPU.md
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[Writing MiniGUI Apps for 64-bit Platforms]: /supplementary-docs/Writing-MiniGUI-Apps-for-64-bit-Platforms.md
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[Quick Start]: /user-manual/MiniGUIUserManualQuickStart.md
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[Building MiniGUI]: /user-manual/MiniGUIUserManualBuildingMiniGUI.md
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[Compile-time Configuration]: /user-manual/MiniGUIUserManualCompiletimeConfiguration.md
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[Runtime Configuration]: /user-manual/MiniGUIUserManualRuntimeConfiguration.md
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[Tools]: /user-manual/MiniGUIUserManualTools.md
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[Feature List]: /user-manual/MiniGUIUserManualFeatureList.md
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[MiniGUI Overview]: /MiniGUI-Overview.md
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[MiniGUI User Manual]: /user-manual/README.md
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[MiniGUI Programming Guide]: /programming-guide/README.md
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[MiniGUI Porting Guide]: /porting-guide/README.md
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[MiniGUI Supplementary Documents]: /supplementary-docs/README.md
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[MiniGUI API Reference Manuals]: /api-reference/README.md
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[MiniGUI Official Website]: http://www.minigui.com
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[Beijing FMSoft Technologies Co., Ltd.]: https://www.fmsoft.cn
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[FMSoft Technologies]: https://www.fmsoft.cn
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[HarfBuzz]: https://www.freedesktop.org/wiki/Software/HarfBuzz/
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