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POCan't detect when Windows Font Size has changed C++ MFC
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copied!<p>I'm trying to determine how I can detect when the user changes the Windows Font Size from Normal to Extra Large Fonts, the font size is selected by executing the following steps on a Windows XP machine:</p> <ol> <li>Right-click on the desktop and select Properties.</li> <li>Click on the Appearance Tab.</li> <li>Select the Font Size: Normal/Large Fonts/Extra Large Fonts</li> </ol> <p>My understanding is that the font size change results in a DPI change, so here is what I've tried so far.</p> <hr> <h2>My Goal:</h2> <p>I want to detect when the <strong>Windows Font Size</strong> has changed from Normal to Large or Extra Large Fonts and take some actions based on that font size change. I assume that when the Windows Font Size changes, the DPI will also change (especially when the size is Extra Large Fonts</p> <hr> <h2>What I've tried so far:</h2> <p>I receive several messages including: WM_SETTINGCHANGE, WM_NCCALCSIZE, WM_NCPAINT, etc... but none of these messages are unique to the situation when the font size changes, in other words, when I receive the WM_SETTINGSCHANGE message I want to know what changed.</p> <p>In theory when I define the OnSettingChange and Windows calls it, the lpszSection should tell me what the changing section is, and that works fine, but then I check the given section by calling SystemParametersInfo and I pass in the action SPI_GETNONCLIENTMETRICS, and I step through the debugger and I make sure that I watch the data in the returned NONCLIENTMETRICS for any font changes, but none occur.</p> <p>Even if that didn't work, I should still be able to check the DPI when the Settings change. I really wouldn't care about the other details, every time I get the WM_SETTINGCHANGE message, I would just check the DPI and perform the actions I'm interested in performing, but I'm not able to get the system DPI either.</p> <p>I have tried to get the DPI by invoking the method GetSystemMetrics, also for each DC:</p> <p>Dekstop DC->GetDeviceCaps LOGPIXELSX/LOGPIXELSY Window DC->GetDeviceCaps LOGPIXELSX/LOGPIXELSY Current DC->GetDeviceCaps LOGPIXELSX/LOGPIXELSY</p> <p>Even if I change the DPI in the Graphic Properties Window these values don't return anything different, they always show 96.</p> <p>Could anybody help me figure this out please? What should I be looking for? Where should I be looking at?</p> <pre><code>afx_msg void CMainFrame::OnSettingChange(UINT uFlags, LPCTSTR lpszSection) { int windowDPI = 0; int deviceDPI = 0; int systemDPI = 0; int desktopDPI = 0; int dpi_00_X = 0; int dpi_01_X = 0; int dpi_02_X = 0; int dpi_03_X = 0; CDC* windowDC = CWnd::GetWindowDC(); // try with window DC HDC desktop = ::GetDC(NULL); // try with desktop DC CDC* device = CWnd::GetDC(); // try with current DC HDC hDC = *device; // try with HDC if( windowDC ) { windowDPI = windowDC->GetDeviceCaps(LOGPIXELSY); // always 96 regardless if I change the Font // Size to Extra Large Fonts or keep it at Normal dpi_00_X = windowDC->GetDeviceCaps(LOGPIXELSX); // 96 } if( desktop ) { desktopDPI = ::GetDeviceCaps(desktop, LOGPIXELSY); // 96 dpi_01_X = ::GetDeviceCaps(desktop, LOGPIXELSX); // 96 } if( device ) { deviceDPI = device->GetDeviceCaps(LOGPIXELSY); // 96 dpi_02_X = device->GetDeviceCaps(LOGPIXELSX); // 96 } systemDPI = ::GetDeviceCaps(hDC, LOGPIXELSY); // 96 dpi_03_X = ::GetDeviceCaps(hDC, LOGPIXELSX); // 96 CWnd::ReleaseDC(device); CWnd::ReleaseDC(windowDC); ::ReleaseDC(NULL, desktop); ::ReleaseDC(NULL, hDC); CWnd::OnWinSettingChange(uFlags, lpszSection); } </code></pre> <p>The DPI always returns 96, but the settings changes DO take effect when I change the font size to Extra Large Fonts or if I change the DPI to 120 (from the graphics properties).</p>

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