Date: Tue, 15 Feb 2005 21:28:48 +0900 (JST) From: "Michael Leonhard" Subject: [SDL] resize bug on Win32 and patch This is my first post to this mailing list. In this email I will detail a bug in the behavior of resizable SDL windows on Win32. Then I will explain the solution and provide a patch. Symptoms: Under Windows, an SDL display created with the SDL_RESIZABLE flag exhibits quirky behavior when being maximized. The window is resized to the proper size, but it is shifted upwards about half the height of the title bar. Similarly, a window whose origin is above the top of the screen will spontaneously move its upper-left origin upon being resized. After two such resize-induced moves, the title bar will be entirely off the top edge of the screen. Subsequently, when the mouse is clicked and released on the window border, the window will shrink its height spontaneously. This height shrinkage occurs even if the user did not resize the border. To observe this curious situation, please invoke: SDL-1.2.8/test/testwm.exe -resize Cause: A pair of integers, SDL_windowX and SDL_windowY, are defined in video/wincommon/SDL_sysevents.c. They are used by the DirectX video driver and the DIB video driver: video/windx5/SDL_dx5video.c video/windib/SDL_dibvideo.c As I understand the source code, the primary use of these variables is to create a rectangle that represents the surface area in CLIENT SPACE. Client space refers to a coordinate system that originates at the upper left corner of a Win32 Window's drawable area. This is just inside the window border and title bar. This client space rectangle, called bounds, is subsequently converted to screen space with a call to AdjustWindowRectEx. The problem is found in SDL's handling of the WM_WINDOWPOSCHANGED message. According to MSDN, "The WM_WINDOWPOSCHANGED message is sent to a window whose size, position, or place in the Z order has changed as a result of a call to the SetWindowPos function or another window-management function." I have confirmed that this message is indeed being sent to the SDL window when the mouse is clicked on the window border, even if the window border is not dragged. In video/wincommon/SDL_sysevents.c, on line 464, in response to the WM_WINDOWPOSCHANGED message, the (potentially) new client rectangle is obtained. This rectangle is translated into screen coordinates and THEN assigned to the SDL_windowX and Y variables. Thus screen coordinates are being assigned to client coordinate variables. Once this is understood, the solution is apparent: assign SDL_windowX and Y before translating the rectangle to screen coordinates. This is accomplished by the following patch. -Mike_L

## Makefile.am for the main() function in the SDL library
#
# This is necessary because some platforms have special program
# entry points, which require special application initialization.

ARCH_SUBDIRS = $(srcdir)/beos \
               $(srcdir)/epoc \
               $(srcdir)/dummy \
               $(srcdir)/macos \
               $(srcdir)/macosx \
               $(srcdir)/qtopia \
               $(srcdir)/win32

# Build a separate library containing the main() entry point.
lib_LIBRARIES = libSDLmain.a

if TARGET_WIN32
MAINLIB_ARCH_SRCS = win32/SDL_win32_main.c
else
if TARGET_MACOSX
if USE_COCOA
MAINLIB_ARCH_SRCS = macosx/SDLMain.m macosx/SDLMain.h
else
if USE_CARBON
MAINLIB_ARCH_SRCS = macos/SDL_main.c
endif # USE_CARBON
endif # USE_COCOA
else
if TARGET_QTOPIA
MAINLIB_ARCH_SRCS = qtopia/SDL_qtopia_main.cc
else
MAINLIB_ARCH_SRCS = dummy/SDL_dummy_main.c
endif # !TARGET_QTOPIA
endif # !TARGET_MACOSX
endif # !TARGET_WIN32
libSDLmain_a_SOURCES = $(MAINLIB_ARCH_SRCS)

# Build an internal library of any special app setup functions
noinst_LTLIBRARIES = libarch.la

if TARGET_BEOS
ARCH_SRCS = beos/SDL_BeApp.cc beos/SDL_BeApp.h
else
ARCH_SRCS = arch.c
endif

libarch_la_SOURCES = $(ARCH_SRCS)

exports:
	for i in $(ARCH_SUBDIRS); do if [ -d $$i/exports ]; then (cd $$i/exports; make); fi; done

# The architecture specific directories need to be copied into place
# when building a distribution.
dist-hook:
	(cd $(distdir) && rm -f $(BUILT_SOURCES))
	cp -rp $(ARCH_SUBDIRS) $(distdir)
	(cd $(distdir) && rm -rf `find . -name CVS`)