<AWT Dev> Fwd: Found and solved a bug on Cursor Management on Windows platforms

[Anthony Petrov]

Hi Morvan,

The IDC_HAND system cursor was introduced in Windows 2000. Java's 
HAND_CURSOR seems to be introduced way before Win2K has been released. 
Hence the need for a custom cursor back in the days. Clearly, this 
doesn't make any sense today. We should switch to using the system 
default cursor for this cursor type.

Would you like to prepare a patch for this issue, test it, and post on 
this mailing list for a review? I know that building JDK on Windows is 
not an easy task, but it can be accomplished nevertheless, and the new 
build system has made it much simpler than it was before. Please refer 
to this document

http://hg.openjdk.java.net/jdk8/build/raw-file/tip/README-builds.html

for build instructions.

--
best regards,
Anthony

On 04/22/2013 08:32 PM, Morvan Le Mescam wrote:
> Dear all,
>
> When developping a Swing client, I face the following problem :
> When setting the hand cursor on Windows, I noticed that the default
> system cursor was not used.
>
> I analysed the problem and found the rrot cause.
> I also made a correction and tested it on Windows 7.
>
> This is my analyse :
>
> When reading Java source code, it is obvious that on Windows, Java does
> not use System resources.
>
> In the code (from *jdk\src\windows\native\sun\windows\awt_Cursor.cpp* )
> bellow :
>
> AwtCursor * AwtCursor::*CreateSystemCursor*(jobject jCursor)
>
> {
>
>      JNIEnv *env = (JNIEnv *)JNU_GetEnv(jvm, JNI_VERSION_1_2);
>
>      jint type = env->GetIntField(jCursor, AwtCursor::typeID);
>
>      DASSERT(type != java_awt_Cursor_CUSTOM_CURSOR);
>
>      LPCTSTR winCursor;
>
>      switch (type) {
>
>        case java_awt_Cursor_DEFAULT_CURSOR:
>
>        default:
>
>          winCursor = IDC_ARROW;
>
>          break;
>
>        case java_awt_Cursor_CROSSHAIR_CURSOR:
>
>          winCursor = IDC_CROSS;
>
>          break;
>
> *[…]*
>
> *case java_awt_Cursor_HAND_CURSOR:*
>
> *winCursor = TEXT("HAND_CURSOR");*
>
> *break;*
>
>        case java_awt_Cursor_MOVE_CURSOR:
>
>          winCursor = IDC_SIZEALL;
>
>          break;
>
>      }
>
> *    HCURSOR hCursor = ::LoadCursor(NULL, winCursor);*
>
>      if (*hCursor == NULL*) {
>
>          /* Not a system cursor, check for resource. */
>
> *hCursor = ::LoadCursor(AwtToolkit::GetInstance().GetModuleHandle(),*
>
> *winCursor);*
>
>      }
>
>      if (hCursor == NULL) {
>
>          hCursor = ::LoadCursor(NULL, IDC_ARROW);
>
> DASSERT(hCursor != NULL);
>
>      }
>
>      AwtCursor *awtCursor = new AwtCursor(env, hCursor, jCursor);
>
>      setPData(jCursor, ptr_to_jlong(awtCursor));
>
>      return awtCursor;
>
> }
>
> In the case of the HAND_CURSOR (*in red*),  Java will try to load the
> cursor from the system (*in blue*).
>
> If it fails (*hCursor == NULL*) then it will try to load the cursor from
> its own resource (*in orange*) :
>
> *hCursor = ::LoadCursor(AwtToolkit::GetInstance().GetModuleHandle(),*
>
> *winCursor);*
>
> In our case, if we check in the AWTToolkit module resources, in
> *jdk\src\windows\native\sun\windows\awr.rc*, we find the following content :
>
> #include "windows.h"
>
> // Need 2 defines so macro argument to XSTR will get expanded before
> quoting.
>
> #define XSTR(x) STR(x)
>
> #define STR(x)  #x
>
> LANGUAGE LANG_NEUTRAL, SUBLANG_NEUTRAL
>
> *HAND_CURSOR  CURSOR DISCARDABLE "hand.cur"*
>
> AWT_ICON ICON    DISCARDABLE "awt.ico"
>
> CHECK_BITMAP BITMAP  DISCARDABLE "check.bmp"
>
> And we find that java.exe embed its own hand cursor, in
> *jdk\src\windows\native\sun\windows\hand.cur* : The “famous” hand that
> it is displayed instead of our system cursor.
>
>
> This is the correction :
>
> , I made the correction into the JRE source code :
>
>        case java_awt_Cursor_HAND_CURSOR:
>
>          /* MLM change winCursor = TEXT("HAND_CURSOR"); */
>
>          winCursor = IDC_HAND;
>
>          break;
>
> I could compile and regenerate a JRE with this change :
>
> D:\Work\Current\openjdk\build\windows-amd64\bin>java -version
>
> openjdk version "1.7.0-u6-unofficial"
>
> OpenJDK Runtime Environment (build 1.7.0-u6-unofficial-b24)
>
> OpenJDK 64-Bit Server VM (build 21.0-b17, mixed mode)
>
> And this works !
>
> If I change the hand cursor at System level, Java takes it into account.
>
> Last but not least question:
>
> Why did a Sun developper, one day : winCursor = TEXT("HAND_CURSOR");
>
> This seems so not consistent with other part of the code... So there is
> probably a good reason. Perhaps the hand cursor was not existant on
> Windows platform when this was done ?
>
>
> Regards
>
>
> Morvan
>
>