X-Git-Url: https://git.artsoft.org/?p=rocksndiamonds.git;a=blobdiff_plain;f=src%2Fgame.c;h=41add9e6745afd10fb6ad28fafe4e438d6aa7e9e;hp=cea1b769be4fd43ad9ece0c2710720b63434caa9;hb=1afe0b4fb9e16c78f2bb810c1225098f5d77e2d3;hpb=8c7cf0796617d786268af85fc5e5f1ad7846f3a1

diff --git a/src/game.c b/src/game.c
index cea1b769..41add9e6 100644
--- a/src/game.c
+++ b/src/game.c
@@ -10252,9 +10252,50 @@ static void HandleElementChange(int x, int y, int page)
     {
       /* !!! not clear why graphic animation should be reset at all here !!! */
       /* !!! UPDATE: but is needed for correct Snake Bite tail animation !!! */
+      /* !!! SOLUTION: do not reset if graphics engine set to 4 or above !!! */
+
+      /*
+	GRAPHICAL BUG ADDRESSED BY CHECKING GRAPHICS ENGINE VERSION:
+
+	When using an animation frame delay of 1 (this only happens with
+	"sp_zonk.moving.left/right" in the classic graphics), the default
+	(non-moving) animation shows wrong animation frames (while the
+	moving animation, like "sp_zonk.moving.left/right", is correct,
+	so this graphical bug never shows up with the classic graphics).
+	For an animation with 4 frames, this causes wrong frames 0,0,1,2
+	be drawn instead of the correct frames 0,1,2,3. This is caused by
+	"GfxFrame[][]" being reset *twice* (in two successive frames) after
+	an element change: First when the change delay ("ChangeDelay[][]")
+	counter has reached zero after decrementing, then a second time in
+	the next frame (after "GfxFrame[][]" was already incremented) when
+	"ChangeDelay[][]" is reset to the initial delay value again.
+
+	This causes frame 0 to be drawn twice, while the last frame won't
+	be drawn anymore, resulting in the wrong frame sequence 0,0,1,2.
+
+	As some animations may already be cleverly designed around this bug
+	(at least the "Snake Bite" snake tail animation does this), it cannot
+	simply be fixed here without breaking such existing animations.
+	Unfortunately, it cannot easily be detected if a graphics set was
+	designed "before" or "after" the bug was fixed. As a workaround,
+	a new graphics set option "game.graphics_engine_version" was added
+	to be able to specify the game's major release version for which the
+	graphics set was designed, which can then be used to decide if the
+	bugfix should be used (version 4 and above) or not (version 3 or
+	below, or if no version was specified at all, as with old sets).
+
+	(The wrong/fixed animation frames can be tested with the test level set
+	"test_gfxframe" and level "000", which contains a specially prepared
+	custom element at level position (x/y) == (11/9) which uses the zonk
+	animation mentioned above. Using "game.graphics_engine_version: 4"
+	fixes the wrong animation frames, showing the correct frames 0,1,2,3.
+	This can also be seen from the debug output for this test element.)
+      */
+
       /* when a custom element is about to change (for example by change delay),
 	 do not reset graphic animation when the custom element is moving */
-      if (!IS_MOVING(x, y))
+      if (game.graphics_engine_version < 4 &&
+	  !IS_MOVING(x, y))
       {
 	ResetGfxAnimation(x, y);
 	ResetRandomAnimationValue(x, y);