Sticky Keys backend

Design task: T42339
Differential Revision: D840
Initial implementation proposal: T41867

Short description:
With this we can distinguish between holding and tabbing a key. Useful
is this if we want to assign to operators to a single shortcut. If two
operators are assigned to one shortcut, we call this a sticky key.

More info is accessible through the design task and the diff.

A few people that were involved with this:
* Sean Olson for stressing me with this burden ;) - It is his enthusiasm
that pushed me forward to get this done
* Campbell and Antony for the code and design review
* Ton for the design review
* All the other people that gave feedback on the patch and helped to
make this possible

A big "Thank You" for you all!

1 files changed, 10 insertions, 7 deletions

diff --git a/source/blender/windowmanager/WM_types.h b/source/blender/windowmanager/WM_types.h
index e716cd6b779..366d3218176 100644
--- a/source/blender/windowmanager/WM_types.h
+++ b/source/blender/windowmanager/WM_types.h
@@ -180,9 +180,11 @@ enum {
 #define KM_NOTHING	0
 #define KM_PRESS	1
 #define KM_RELEASE	2
-#define KM_CLICK	3
-#define KM_DBL_CLICK	4
 
+/* clicktype */
+#define KM_CLICK     3 /* clicked key (click_time <= U.click_timeout) */
+#define KM_DBL_CLICK 4 /* double click - keep at 4 to avoid breakage with older key configs */
+#define KM_HOLD      5 /* held key    (click_time >  U.click_timeout) */
 
 /* ************** UI Handler ***************** */
 
@@ -427,7 +429,9 @@ typedef struct wmEvent {
 	
 	short type;			/* event code itself (short, is also in keymap) */
 	short val;			/* press, release, scrollvalue */
+	short click_type;	/* click, hold or double click */
 	int x, y;			/* mouse pointer position, screen coord */
+	double click_time;	/* the time since keypress started */
 	int mval[2];		/* region mouse position, name convention pre 2.5 :) */
 	char utf8_buf[6];	/* from, ghost if utf8 is enabled for the platform,
 						 * BLI_str_utf8_size() must _always_ be valid, check
@@ -435,20 +439,19 @@ typedef struct wmEvent {
 	char ascii;			/* from ghost, fallback if utf8 isn't set */
 	char pad;
 
-	/* previous state, used for double click and the 'click' */
+	bool is_key_pressed; /* is a (non-modifier) key is pressed? (keyboard, mouse, NDOF, ...) */
+
+	/* previous state, used for clicktype */
 	short prevtype;
 	short prevval;
 	int prevx, prevy;
-	double prevclicktime;
+	double prevclick_time;
 	int prevclickx, prevclicky;
 	
 	/* modifier states */
 	short shift, ctrl, alt, oskey;	/* oskey is apple or windowskey, value denotes order of pressed */
 	short keymodifier;				/* rawkey modifier */
 	
-	/* set in case a KM_PRESS went by unhandled */
-	short check_click;
-	
 	/* keymap item, set by handler (weak?) */
 	const char *keymap_idname;