Found and solved a bug on Cursor Management on Windows platforms

[Anthony Petrov]

Hi Morvan,

build-dev@ is the wrong mailing list for this topic. It belongs to 
awt-dev at openjdk.java.net only. Please re-post this message there.

--
best regards,
Anthony

On 04/17/2013 09:01 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
>