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249 lines
9.1 KiB
Markdown
249 lines
9.1 KiB
Markdown
# Scroll Window Control
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Scroll window (ScrollWnd) control is a container control with scroll bars to
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browse children windows in it. Its basic usage is to place child controls, so
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make the user can check and operate many controls in a window by scroll bars.
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Certainly, `ScrollWnd` can also be used to do many other things, and it is easy
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to be customized. In the end of this chapter, we will see a example which uses
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`ScrollWnd` as a picture viewer.
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In an application, calling `CreateWindow` function with `CTRL_SCROLLWND` as the
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control class name can create `ScrollWnd` control.
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## Scrollable Window
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`ScrollWnd` control and `ScrollView` control discussed in the next chapter are
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both scrollable window controls, and have many similarities. A scrollable
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window comprises a control window (visible area) with scroll bar and content
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area, as shown in Figure 1. When scroll bar is used to move the display content
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area, horizontal position value or vertical position value of content area will
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change. Size of content area can be controlled by application, but cannot be
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smaller than visible area.
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Figure 1 A scrollable window
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## General Scroll Window Messages
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`ScrollWnd` and `ScrollView` control all respond to some general scroll window
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messages, including getting and setting content range of scroll window, setting
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scroll value of scroll bar, getting and setting the current position of content
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area, getting and setting size of visible area, etc.
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### Get/Set the Range of Content Area and Visible Area
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`SVM_SETCONTRANGE` message is used to set the size of the content area of a
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scroll window:
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```
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```
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Here, `cont_w` and `cont_h` are the width and the height of content area to be
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set respectively. If `cont_w` or `cont_h` is negative, content area will not
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change; if the content area width (height) to be set is less than visible area
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width (height), the content area width (height) after set will equal to the
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visible area width (height).
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`SVM_SETCONTWIDTH` message and `SVM_SETCONTHEIGHT` message are used to set the
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width and the height of a scroll window respectively:
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```
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```
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`SVM_GETCONTWIDTH`, `SVM_GETCONTHEIGHT`, `SVM_GETVISIBLEWIDTH` and
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`SVM_GETVISIBLEHEIGHT` message are used to get the content area width and
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height and the visible area width and height respectively.
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### Get Position Information and Set Current Position
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`SVM_GETCONTENTX` and `SVM_GETCONTENTY` messages are used to get the current
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position value of the content area:
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```
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```
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`SVM_SETCONTPOS` message is used to set the current position value of the
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content area, i.e. move the content area to a specified position in the visible
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area:
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```
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```
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`SVM_MAKEPOSVISIBLE` message is used to make a position point in the content
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area visible:
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```
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```
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If this position point is invisible originally, while it becomes visible by
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using `SVM_MAKEPOSVISIBLE` message, the position point will locate in the up
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edge of visible area (previous position point is above visible area) or down
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edge of visible area (previous position point is below visible area).
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### Get/Set Scroll Properties
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`SVM_GETHSCROLLVAL` and `SVM_GETVSCROLLVAL` messages are used to get the
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current horizontal and vertical line values of the scroll window (the scroll
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values when clicking the scroll arrow); `VM_GETHSCROLLPAGEVAL` and
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`SVM_GETVSCROLLPAGEVAL` messages are used to get the current horizontal and
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vertical page values of the scroll window (the scroll values when clicking the
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scroll page):
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```
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```
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`SVM_SETSCROLLVAL` message is used to set the horizontal and (or) vertical line
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value of a scroll window; `wParam` argument is the horizontal line value and
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`lParam` is the vertical line value; if the horizontal (vertical) line value is
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zero or negative value, the current horizontal (vertical) line value of the
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scroll window will not change:
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```
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```
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`SVM_SETSCROLLPAGEVAL` is used to set the horizontal and (or) vertical page
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value of a scroll window; `wParam` argument is the horizontal page value and
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`lParam` is the vertical page value; if the horizontal (vertical) page value is
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zero or negative value, the current horizontal (vertical) page value of the
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scroll window will not change:
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```
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```
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## Message of Scroll Window Control
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### Add Child Control
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```
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```
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It should be noted that adding controls to `ScrollWnd` control will not change
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the content area range of the scroll window, and if the position of a child
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control locates beyond the current range of the content area, you cannot see
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the control in the content area. Therefore, generally, you should use
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`SVM_SETCONTRANGE` message to set the range of the content area before adding
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child controls, to make it suitable for display of controls to be added.
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Except sending `SVM_ADDCTRLS` message to add child controls after `ScrollWnd`
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control is created, you can also make `ScrollWnd` automatically add the child
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controls after passing the pointer to a `CONTAINERINFO` structure in
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`dwAddData` argument, when calling `CreateWindow` function to create the
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`ScrollWnd` control creates `ScrollWnd:`
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```
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```
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The field controlnr is the number of controls, controls points to a `CTRLDATA`
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control array; Additional data is passed through `dwAddData` field in
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`CONTAINERINFO` structure.
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`SVM_RESETCONTENT` message is used to reset a `ScrollWnd` control, including
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destroying its child controls and set the range and the position values of the
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content area to be the default values:
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```
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```
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### Get Handle of Child Control
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`SVM_GETCTRL` can be used to get the handle of a child control in a `ScrollWnd`
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control:
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```
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```
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`SVM_GETFOCUSCHILD` message can be used to get the child control gaining
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keyboard focus in a `ScrollWnd` control:
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```
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```
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### Container (Content) Window Procedure
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The window in which child control is contained in a scroll window is called the
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container window, i.e. content window (area). You can use
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`SVM_SETCONTAINERPROC` message to set a new container window procedure, to
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achieve the goal of customizing the scroll window for an application:
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```
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```
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The parameter `lParam` is the container window process defined by your
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application, and this window procedure should call the default container window
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procedure function `DefaultContainerProc` by default:
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```
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```
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Additionally, an application can specify user-defined container window
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procedure by `user_proc` field of `CONTAINERINFO` aforementioned.
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## Sample Program
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We illustrate the method of using `ScrollWnd` control to construct a simple
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picture viewer using code in List 1. Please refer to scrollwnd.c program in
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this guide sample program packet `mg-samples` for the complete source code of
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this program.
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List 1 Example program for `ScrollWnd` control
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```
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```
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This simple picture viewer can be used to view a picture by using scrollbar,
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and to enlarge and shrink the picture. The picture viewer sets a new container
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window procedure function by sending `SVM_SETCONTAINERPROC` message, and draws
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the picture in `MSG_PAINT` message.Running effect of the program is shown as
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Figure 2.
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Figure 2 A simple picture explorer
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-- Main.XiaodongLi - 26 Oct 2009
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----
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[<< ](MiniGUIProgGuidePart.md) |
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[Table of Contents](README.md) |
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[ >>](MiniGUIProgGuidePart.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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