How to create semi-transparent windows using Symbian C++

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Article Metadata
Code ExampleCompatibilityArticle
Keywords: CControlOnTopCtrl
Created: chenziteng (27 Sep 2009)
Last edited: hamishwillee (17 Sep 2012)



This article describes how to create semi-transparent windows on devices support display mode EColor16MA.


The device must support display mode EColor16MA, the display mode can be checked the following code

// EColor16MA is supported


The solution is from the "Semi-Transparent Windows" series of articles by william.edwards (the UIQ developer website has been closed but you can open the cached pages after Googling the keywords "Semi-Transparent Windows #1" and "Semi-Transparent Windows #2").

void CControlOnTopCtrl::ConstructL(const TRect& aRect, RWindowGroup* aWindowGroup)
TRect rc(aRect);
TInt w = rc.Width();
TInt h = rc.Height();
for (TInt i = 0; i < 2; i++)
w /= 2;
h /= 2;
TRect rc_new(w, h, w+15, h+15);
// begin by chen, code from William's post
// we need to set the display mode to ensure that it has an
// alpha-component specified. However, the system may instead return
// another display mode. We don't have to pay much attention, as the
// call to SetTransparencyAlphaChannel will check wether the Window
// Server and the window's display mode support this kind of
// transparency
TRgb backgroundColour = KRgbWhite; // for example
if(KErrNone == Window().SetTransparencyAlphaChannel())
// we now have a semi-transparent window,
// so we have to not clear the window region in an
// opaque colour before drawing it each time;
// 0 alpha is completely transparent,
// 255 alpha is completely opaque
// end by chen

The code has been verified on S60 5th Edition emulator and a device that support EColor16MA, see the emulator screenshots (a transparent window with a red dot):

Semi-transparent03.PNG Semi-transparent04.PNG

The full example can be download: HelloWorld(Semi-transparent).zip

Version Hint

Windows Phone: [[Category:Windows Phone]]
[[Category:Windows Phone 7.5]]
[[Category:Windows Phone 8]]

Nokia Asha: [[Category:Nokia Asha]]
[[Category:Nokia Asha Platform 1.0]]

Series 40: [[Category:Series 40]]
[[Category:Series 40 1st Edition]] [[Category:Series 40 2nd Edition]]
[[Category:Series 40 3rd Edition (initial release)]] [[Category:Series 40 3rd Edition FP1]] [[Category:Series 40 3rd Edition FP2]]
[[Category:Series 40 5th Edition (initial release)]] [[Category:Series 40 5th Edition FP1]]
[[Category:Series 40 6th Edition (initial release)]] [[Category:Series 40 6th Edition FP1]] [[Category:Series 40 Developer Platform 1.0]] [[Category:Series 40 Developer Platform 1.1]] [[Category:Series 40 Developer Platform 2.0]]

Symbian: [[Category:Symbian]]
[[Category:S60 1st Edition]] [[Category:S60 2nd Edition (initial release)]] [[Category:S60 2nd Edition FP1]] [[Category:S60 2nd Edition FP2]] [[Category:S60 2nd Edition FP3]]
[[Category:S60 3rd Edition (initial release)]] [[Category:S60 3rd Edition FP1]] [[Category:S60 3rd Edition FP2]]
[[Category:S60 5th Edition]]
[[Category:Symbian^3]] [[Category:Symbian Anna]] [[Category:Nokia Belle]]

This page was last modified on 17 September 2012, at 07:27.
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