Fixed bugs #882 and 865, re-opening bug #634 SDL-1.2
authorSam Lantinga <slouken@libsdl.org>
Tue, 17 Nov 2009 04:59:13 +0000
branchSDL-1.2
changeset 4384 6800e2560310
parent 4383 daf9e6037596
child 4385 a2bb14457446
Fixed bugs #882 and 865, re-opening bug #634

Ronald Lamprecht to SDL

Hi,

Sam Lantinga wrote:

The problem with that fix is that it breaks IME events again. Maybe
we can handle keyboard events differently to prevent this issue?


Spending an hour reading MSDN, analysing SDL and another hour testing the reality on XP I am really wondering how patch r4990 could have ever worked in any situation. It's main effect is to break the unicode translation and causing spurious activation events!

Why does TranslateMessage(&msg) nothing useful? Simply because it does not affect "msg" at all! All keyboard events are dispatched without the slightest change (see MSDN). TranslateMessage() just appends additional WM_CHAR, WM_DEADCHAR, WM_SYSCHAR, WM_SYSDEADCHAR event messages to the queue. But I could not find any SDL event handling routine that catches these events and transforms them to proper SDL keyevents while eliminating the corresponding WM_KEYDOWN, etc. events. Thus any IME input like the '@' generated by "Alt + 6(Numpad) + 4(Numpad)" is simply lost.

But the situation is even worse! Up to r4990 the TranslateKey()/ToUnicode() calls did evaluate dead keys and did deliver proper key events for subsequent key strokes like '´' + 'e' resulting in 'é'. ToUnicode() needs proper key state informations to be able to handle these substitutions. But unfortunatly TranslateMessage() needs the same state information and eats it up while generating the WM_CHAR messages :-( Thus the current 1.2.14 breakes the partial IME support of previous releases, too.

The key state race condition between ToUnicode() and TranslateMessage() requires to avoid any ToUnicode() usage for receiving proper WM_CHAR, etc. messages generated by TranslateMessage(). (Yes - the '@' and 'é' appear as WM_CHAR messages when unicode is switched off).

The spurious SDL activation events are *not* caused by additional WM_ACTIVATE Windows messages! Besides DIB_HandleMessage() SDL_PrivateAppActive() is called by another source which I am not yet aware of - any hints?

Thus I do strongly recommend the deletion of the TranslateMessage(&msg) call as a quick fix.

A proper support of unicode and IME requires a clean SDL keyboard input concept first. Which SDL keyboards events should be transmitted to the app when the user presses '´' + 'e' ? Within the current unicode handling the first key stroke is hidden. Even though ToUnicode() delivers the proper key SDL does ignore it in TranslateKey(). Just the composed key event is transmitted to the app. That is what you expect for text input, but the app can no longer use keys like '^' as a key button because it will never receive a key event for it!

With a given concept it seems to be necessary to regenerate SDL key events out of the WM_CHAR, etc. events and to drop all related direct WM_KEYDOWN, etc. events while the remaining basic WM_KEYDOWN, etc. events would still have to result in SDL key events.

Anyway the source of the spurious WM_ACTIVATE should be located to avoid future trouble.

Greets,

Ronald
src/video/windib/SDL_dibevents.c
src/video/windx5/SDL_dx5events.c
--- a/src/video/windib/SDL_dibevents.c	Sun Nov 15 17:21:24 2009 +0000
+++ b/src/video/windib/SDL_dibevents.c	Tue Nov 17 04:59:13 2009 +0000
@@ -198,7 +198,7 @@
 				m.wParam = wParam;
 				m.lParam = lParam;
 				m.time = 0;
-				if ( PeekMessage(&m, hwnd, 0, WM_USER, PM_NOREMOVE) && (m.message == WM_CHAR) ) {
+				if ( TranslateMessage(&m) && PeekMessage(&m, hwnd, 0, WM_USER, PM_NOREMOVE) && (m.message == WM_CHAR) ) {
 					GetMessage(&m, hwnd, 0, WM_USER);
 			    		wParam = m.wParam;
 				}
@@ -363,7 +363,6 @@
 
 	while ( PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE) ) {
 		if ( GetMessage(&msg, NULL, 0, 0) > 0 ) {
-			TranslateMessage(&msg);
 			DispatchMessage(&msg);
 		}
 	}
--- a/src/video/windx5/SDL_dx5events.c	Sun Nov 15 17:21:24 2009 +0000
+++ b/src/video/windx5/SDL_dx5events.c	Tue Nov 17 04:59:13 2009 +0000
@@ -657,7 +657,6 @@
 	while ( ! posted &&
 	        PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE) ) {
 		if ( GetMessage(&msg, NULL, 0, 0) > 0 ) {
-			TranslateMessage(&msg);
 			DispatchMessage(&msg);
 		} else {
 			return(-1);
@@ -716,17 +715,12 @@
 	}
 	if ( event != WAIT_TIMEOUT ) {
 		/* Maybe there was a windows message? */
-		posted = 0;
-		while ( ! posted &&
-			PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE) ) {
+		if ( PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE) ) {
 			if ( GetMessage(&msg, NULL, 0, 0) > 0 ) {
-				TranslateMessage(&msg);
 				DispatchMessage(&msg);
 			} else {
 				return(-1);
 			}
-		}
-		if ( posted ) {
 			return(1);
 		}
 	}