BUG: Graphics Operations Consume GDI Memory (98058)
The information in this article applies to:
- Microsoft Windows Software Development Kit (SDK) 3.1
This article was previously published under Q98058
3.10
WINDOWS
kbprg kbbuglist
SYMPTOMS
In the Microsoft Windows graphical operating environment, when a device
driver has rectangle capabilities (such as the 8514/a display driver) and
an application draws many large graphic objects, memory in the GDI data
segment is lost. Eventually, GDI runs out of memory and Windows crashes.
CAUSE
GDI allocates a block of memory and then checks to see whether the device
has rectangle capabilities. If the device does have rectangle capabilities,
GDI calls into the device to let it do the drawing and does not free the
allocated memory.
STATUSMicrosoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article. MORE INFORMATION
If the device does not have rectangle capabilities (for example, the
standard VGA display driver), GDI performs the drawing and frees the
memory. If an application is consuming GDI resources, run the application
on a machine with a VGA display. If GDI resources are not being consumed on
a VGA, then it is quite likely that the application has encountered this
bug.
Under certain circumstances, the following Windows application programming
interfaces (APIs) may encounter this problem:
Drawing functions:
<B>Arc</B>, <B>Chord</B>, <B>Ellipse</B>, <B>Pie</B>, <B>Rectangle</B>, <B>RoundRect</B>
Region functions:
<B>CreateEllipticRgn</B>, <B>CreateEllipiticRgnIndirect</B>, <B>CreateRoundRectRgn</B>
Third-party display-driver developers can avoid the GDI bug by not claiming
rectangle capabilities in the display driver. Just do not set the
PC_RECTANGLE bit in the dpPolygonals member of GDIINFO, and then rebuild the driver.
Applications developers can use several approaches to avoid the problem
code. One approach is to create a memory device context (DC) and use it
instead of the display DC in the GDI functions. When complete, BitBlt the
memory DC to the screen DC. When using a compatible memory DC, the bug is
avoided because GDI performs the drawing instead of the driver.
The following code fragment demonstrates this approach:
hMemDC = CreateCompatibleDC(hDC);
hBitmap = CreateCompatibleBitmap(hDC, width, height);
hOldBitmap = SelectObject(hMemDC, hBitmap);
PatBlt(hMemDC, 0, 0, width, height, WHITENESS);
/***
Use hMemDC in all the GDI functions
.
.
.
***/
BitBlt(hDC, 0, 0, width, height, hMemDC, 0, 0, SRCCOPY);
SelectObject(hMemDC, hOldBitmap);
DeleteObject(hBitmap);
DeleteDC(hMemDC);
The functions PatBlt, MoveTo/LineTo, Polyline, and FillRect are safe alternatives to the drawing functions.
| Modification Type: | Major | Last Reviewed: | 6/18/1999 |
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| Keywords: | kbbug KB98058 |
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