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Revision as of 09:01, 21 June 2012 by hamishwillee (Talk | contribs)

Archived:Drawing with monochrome masks may produce incorrect results on S60 3rd Edition FP2 (Known Issue)

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Archived.pngArchived: This article is archived because it is not considered relevant for third-party developers creating commercial solutions today. If you think this article is still relevant, let us know by adding the template {{ReviewForRemovalFromArchive|user=~~~~|write your reason here}}.

Drawing masked bitmaps using a monochrome (1 bit per pixel) bitmap as a mask may produce incorrect output on S60 3rd Edition, Feature Pack 2 devices.

Article Metadata
Tested with
Devices(s): Reported against Nokia N85, Nokia N96
Compatibility
Platform(s): S60 3rd Edition, Feature Pack 2
S60 3rd Edition FP2
Article
Keywords: BitBltMasked, EGray2
Created: User:Technical writer 1 (11 Nov 2008)
Last edited: hamishwillee (21 Jun 2012)

How to reproduce

Create or load a bitmap (CFbsBitmap) with the same colour depth as the screen device (screen display mode, typically EColor16MU) and an accompanying monochrome bitmap (display mode EGray2) with the identical size.

Draw the bitmap using a masked blit as follows:

 void CMyContainerControl::Draw( const TRect& aRect ) const
{
CWindowGc& gc = SystemGc();
TRect rect( Rect() );
gc.BitBltMasked(rect.iTl, iBitmapEColor16MU, rect, iMaskEGray2, EFalse);
}

On some devices, such as the Nokia N85, the monochrome mask does not work correctly but displays vertical stripes instead.

Solution

This problem does not occur when using masks with the colour depth identical to the parent bitmap. However, this consumes significantly more RAM memory compared to using 1-bpp monochrome bitmaps.

However, inverting the monochrome mask seems to produce correct results:

   gc.BitBltMasked(rect.iTl, iBitmapEColor16MU, rect, iMaskEGray2, '''ETrue''');

As a workaround for monochrome bitmaps, each mask could be inverted and drawn with the 5th parameter of BitBltMasked() (aInvertMask) set to ETrue.

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