cocoa_common: fix crash with dead key input and simplify related code

Fixes #29. When a user used dead input keys (like the accent key), `mpv`
crashed because the code tried to access the 0 element of a characters array
(which was empty).

While I was closing this bug, I refactored some related conditionals to
make the code more readable.

1 files changed, 20 insertions, 9 deletions

diff --git a/video/out/cocoa_common.m b/video/out/cocoa_common.m
index fd8e43b18b..4d4d7f927b 100644
--- a/video/out/cocoa_common.m
+++ b/video/out/cocoa_common.m
@@ -51,9 +51,21 @@
 #define NSOpenGLProfileVersion3_2Core 0x3200
 #endif
 
-#define NSLeftAlternateKeyMask (0x000020 | NSAlternateKeyMask)
+#define NSLeftAlternateKeyMask  (0x000020 | NSAlternateKeyMask)
 #define NSRightAlternateKeyMask (0x000040 | NSAlternateKeyMask)
 
+static bool LeftAltPressed(NSEvent *event)
+{
+    return ([event modifierFlags] & NSLeftAlternateKeyMask) ==
+            NSLeftAlternateKeyMask;
+}
+
+static bool RightAltPressed(NSEvent *event)
+{
+    return ([event modifierFlags] & NSRightAlternateKeyMask) ==
+            NSRightAlternateKeyMask;
+}
+
 // add methods not available on OSX versions prior to 10.7
 #ifndef MAC_OS_X_VERSION_10_7
 @interface NSView (IntroducedInLion)
@@ -678,22 +690,21 @@ void create_menu()
 
 - (void)keyDown:(NSEvent *)theEvent
 {
-    unsigned char charcode;
-    if (([theEvent modifierFlags] & NSRightAlternateKeyMask) ==
-            NSRightAlternateKeyMask)
-        charcode = *[[theEvent characters] UTF8String];
+    NSString *chars;
+
+    if (RightAltPressed(theEvent))
+        chars = [theEvent characters];
     else
-        charcode = [[theEvent charactersIgnoringModifiers] characterAtIndex:0];
+        chars = [theEvent charactersIgnoringModifiers];
 
-    int key = convert_key([theEvent keyCode], charcode);
+    int key = convert_key([theEvent keyCode], *[chars UTF8String]);
 
     if (key > -1) {
         if ([theEvent modifierFlags] & NSShiftKeyMask)
             key |= MP_KEY_MODIFIER_SHIFT;
         if ([theEvent modifierFlags] & NSControlKeyMask)
             key |= MP_KEY_MODIFIER_CTRL;
-        if (([theEvent modifierFlags] & NSLeftAlternateKeyMask) ==
-                NSLeftAlternateKeyMask)
+        if (LeftAltPressed(theEvent))
             key |= MP_KEY_MODIFIER_ALT;
         if ([theEvent modifierFlags] & NSCommandKeyMask)
             key |= MP_KEY_MODIFIER_META;