160 lines
6.9 KiB
Plaintext
160 lines
6.9 KiB
Plaintext
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Theme Aware Controls - 08/03/00
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-------------------------------
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HOW TO MAKE CONTROLS/WINDOWS THEME AWARE
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Here are the high-level steps needed to make a control theme-aware:
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Preparation
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a. The control author decides which aspects of the control will be
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theme aware.
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b. He then divides the control up into 1 or more
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named theme-aware child parts (drawn shapes with optional text).
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c. For each part, the author can define 1 or more background images
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in a single bitmap file. These difference backgrounds are usually
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associated with different states in the control but don't have to
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be. At run time, the appropriate image can be selected using an
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"iStateId" value as the 1-based index to the correct image.
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d. alternatively, the author can decide the create the background based
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on a border color/style/size and a fill color/style.
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e. other ways of rendering may be defined in the future; try to keep
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your control as isolated as possible from the particular theme properties
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and try to use the theme drawing API's exclusively.
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f. the control author then publishes the theme schema for his control. If the control is
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part of comctrls v6, then the schema is added to the file "TmSchema.h"; otherwise,
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the control creates his own "xxxSchema.h" file (which needs to get compiled into
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his control as well as registered with the theme manager).
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g. add schema info:
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- he adds a parts enum to the schema file; ex:
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BEGIN_TM_CLASS_PARTS(EDIT)
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TM_PART(EP, EDITTEXT)
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TM_PART(EP, CARET)
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END_TM_CLASS_PARTS()
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- for each part that has more than 1 state, he adds a state enum:
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BEGIN_TM_PART_STATES(EDITTEXT)
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TM_STATE(ETS, NORMAL)
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TM_STATE(ETS, HOT)
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TM_STATE(ETS, SELECTED)
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TM_STATE(ETS, DISABLED)
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TM_STATE(ETS, FOCUSED)
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TM_STATE(ETS, READONLY)
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TM_STATE(ETS, ASSIST)
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END_TM_PART_STATES()
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h. note that once "TmSchema.h" has been edited, the "\nt\shell\published\inc" directory
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must be built so that the "TmSchema.h" file is copied to "\nt\public\sdk\inc".
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Code Changes
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a. obtain an HTHEME handle to call thememgr drawing routines with. this should
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be done during control creation (as soon as the "hwnd" is available).
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The code for the button control would look something like this:
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HTHEME hTheme;
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hTheme = OpenThemeData(hwnd, L"button");
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if (! hTheme) // fall back on old drawing code...
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{
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}
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b. when its time to paint one of the parts of the control:
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i. first initialize the control's DC; most controls send a WM_CTLCOLORXXX
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msg to their parent to do this. Use the HBRUSH returned from the WM_CTLCOLORXXX
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msg as the DefaultBrush passed to the theme drawing routines.
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ii. pass "hTheme" and the DefaultBrush to the theme drawing routines to paint
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the background, text, line, border, etc. The routines will ensure that the
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painting is done in a theme-compliant way.
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The code for drawing the a push button background would look something like:
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//---- initialize the DC & get DefaultBrush ----
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HBRUSH hDefaultBrush = (HBRUSH)SendMessage(GetParent(hwnd), WM_CTLCOLORBTN, (WPARAM)hdc, (LPARAM)hwnd);
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if (hTheme)
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{
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int iStateId;
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if (fPushed)
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iStateId = 4;
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else if (fDisabled)
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iStateId = 3;
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else if (fMouseOver)
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iStateId = 2;
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else if (fDefault)
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iStateId = 1;
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else
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iStateId = 0;
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//---- DrawThemeBackground doesn't yet accept the hDefaultBrush param ----
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hr = DrawThemeBackgound(hTheme, hdc, TMT_BUTTON, iStateId, &clientRect, 0);
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}
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else // old drawing code
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{
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}
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c. when a WM_THEMECHANGED msg is received by the control/window, it must close its
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current HTMEME handle, try to obtain a new handle, and repaint its control.
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The code would look something like:
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CloseThemeData(hTheme);
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hTheme = OpenThemeData(hwnd, L"BUTTON");
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InvalidateRect(hwnd, NULL, TRUE);
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d. The ThemeRender object should be able to handle most or all of the
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drawing for the control. However, when the control needs to access
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some theme information directly, the programmer can pass the "hTheme"
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handle to one of the theme info "getter" routines. For example, the
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code to get the FONT for a part would look something like:
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if (hTheme)
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{
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LOGFONT *pFont;
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hr = GetThemeFont(hTheme, TMBU_BUTTON, 0, pvFONT, &pFont);
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if (SUCCEEDED(hr))
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{
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<use the pFont here...>
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}
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}
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e. Since its possible that the control's main background may contain
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transparent parts, the programmer will need to handle the WM_NCHITTEST msg
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processing. The code would look something like this:
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if ((msg == WM_NCHITTEST) && (hTheme))
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{
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int val = DefWindowProc(msg, hwnd, wparam, lparam);
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if (val == HTCLIENT) // test further
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{
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BOOL fHit;
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hr = HitTestThemeBackground(hTheme, hdc, TMBU_BUTTON, 0, iStateIndex,
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&clientRect, &fHit);
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if ((SUCCEEDED(hr)) && (! fHit))
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val = HTTRANSPARENT;
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}
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return val;
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}
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f. The programmer needs to be aware that being themed can change the size of
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various parts. For example, a background that used to have a 2-pixel border
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around it may now use a 6-pixel border. The programmer should use methods
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like "GetThemeBackgroundContentRect()" to determine which parts of the background
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content can be put into and "GetThemeTextExtent()" to find out how much space
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the text needs in its theme-selected font.
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