Add better scroll wheel support and option to disable acceleration

runtime/doc/gui_mac.txt

@@ -283,8 +283,6 @@ as general information regarding macOS user defaults.
 Here is a list of relevant dictionary entries:
 
 KEY				VALUE ~
-*MMAllowForceClickLookUp*	use Force click for data lookup instead of
-				<ForceClick> [bool]
 *MMCellWidthMultiplier*		width of a normal glyph in em units [float]
 *MMCmdLineAlignBottom*		Pin command-line to bottom of MacVim [bool]
 *MMDialogsTrackPwd*		open/save dialogs track the Vim pwd [bool]
@@ -307,7 +305,6 @@ KEY				VALUE ~
 *MMTitlebarAppearsTransparent*	enable a transparent titlebar [bool]
 *MMAppearanceModeSelection*	dark mode selection (|macvim-dark-mode|)[bool]
 *MMRendererClipToRow*		clip tall characters to the row they are on [bool]
-*MMScrollOneDirectionOnly*	scroll along one axis only when using trackpad [bool]
 *MMSmoothResize*		allow smooth resizing of MacVim window [bool]
 *MMShareFindPboard*		share search text to Find Pasteboard [bool]
 *MMTextInsetBottom*		text area offset in pixels [int]
@@ -316,12 +313,22 @@ KEY				VALUE ~
 *MMTextInsetTop*		text area offset in pixels [int]
 *MMTexturedWindow*		use brushed metal window (Tiger only) [bool]
 *MMTranslateCtrlClick*		interpret ctrl-click as right-click [bool]
-*MMUseMouseTime*		use mousetime to detect multiple clicks [bool]
 *MMVerticalSplit*		files open in vertical splits [bool]
 *MMZoomBoth*			zoom button maximizes both directions [bool]
 *MMUpdaterPrereleaseChannel*	opt-in to pre-release software update [bool]
 *MMShowWhatsNewOnStartup*	show "What's New" after updating to new version [bool]
 
+Mouse / Trackpad ~
+*MMScrollOneDirectionOnly*	scroll along one axis only when using trackpad [bool]
+*MMAllowForceClickLookUp*	use Force click for data lookup instead of
+				<ForceClick> [bool]
+*MMMouseWheelDisableAcceleration* disable OS scroll wheel acceleration [bool]
+*MMMouseWheelNumLines*		how many lines to scroll when scroll wheel
+				acceleration is turned off [int]
+*MMMouseWheelMinLines*		min number of lines to scroll per scroll wheel
+				click when acceleration is on [int]
+*MMUseMouseTime*		use mousetime to detect multiple clicks [bool]
+
 Tabs ~
 *MMTabColorsMode*		use default/auto/colorscheme for tab colors [int]
 *MMWindowUseTabBackgroundColor*	use tabs background fill color as window color [bool]

runtime/doc/tags

@@ -5654,6 +5654,9 @@ MMFullScreenFadeTime	gui_mac.txt	/*MMFullScreenFadeTime*
 MMLoginShell	gui_mac.txt	/*MMLoginShell*
 MMLoginShellArgument	gui_mac.txt	/*MMLoginShellArgument*
 MMLoginShellCommand	gui_mac.txt	/*MMLoginShellCommand*
+MMMouseWheelDisableAcceleration	gui_mac.txt	/*MMMouseWheelDisableAcceleration*
+MMMouseWheelMinLines	gui_mac.txt	/*MMMouseWheelMinLines*
+MMMouseWheelNumLines	gui_mac.txt	/*MMMouseWheelNumLines*
 MMNativeFullScreen	gui_mac.txt	/*MMNativeFullScreen*
 MMNoFontSubstitution	gui_mac.txt	/*MMNoFontSubstitution*
 MMNoTitleBarWindow	gui_mac.txt	/*MMNoTitleBarWindow*

src/MacVim/Base.lproj/Preferences.xib

@@ -573,11 +573,11 @@
             <point key="canvasLocation" x="137.5" y="478.5"/>
         </customView>
         <customView id="Bnq-Nx-GJH" userLabel="Input">
-            <rect key="frame" x="0.0" y="0.0" width="483" height="110"/>
+            <rect key="frame" x="0.0" y="0.0" width="483" height="155"/>
             <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
             <subviews>
                 <customView id="DAP-Yi-QU0" userLabel="Trackpad">
-                    <rect key="frame" x="20" y="72" width="433" height="18"/>
+                    <rect key="frame" x="20" y="117" width="433" height="18"/>
                     <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                     <subviews>
                         <textField focusRingType="none" verticalHuggingPriority="750" horizontalCompressionResistancePriority="250" id="f18-Wr-EgZ">
@@ -604,11 +604,11 @@
                     </subviews>
                 </customView>
                 <customView id="GZa-RH-fza" userLabel="Mouse">
-                    <rect key="frame" x="20" y="46" width="433" height="18"/>
+                    <rect key="frame" x="20" y="46" width="433" height="63"/>
                     <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                     <subviews>
                         <textField focusRingType="none" verticalHuggingPriority="750" horizontalCompressionResistancePriority="250" id="3Tx-8j-zQR">
-                            <rect key="frame" x="-2" y="0.0" width="187" height="17"/>
+                            <rect key="frame" x="-2" y="45" width="187" height="17"/>
                             <autoresizingMask key="autoresizingMask" flexibleMinY="YES"/>
                             <textFieldCell key="cell" sendsActionOnEndEditing="YES" alignment="right" title="Mouse:" id="imK-Tr-YuD">
                                 <font key="font" metaFont="system"/>
@@ -617,7 +617,7 @@
                             </textFieldCell>
                         </textField>
                         <button id="RLs-2Z-8PJ" userLabel="Ctrl-click as right-click">
-                            <rect key="frame" x="189" y="-1" width="199" height="18"/>
+                            <rect key="frame" x="189" y="44" width="199" height="18"/>
                             <autoresizingMask key="autoresizingMask" flexibleMinY="YES"/>
                             <buttonCell key="cell" type="check" title="Treat Ctrl-click as right-click" bezelStyle="regularSquare" imagePosition="left" alignment="left" inset="2" id="PYG-cd-wzL" userLabel="Ctrl-click as right-click">
                                 <behavior key="behavior" changeContents="YES" doesNotDimImage="YES" lightByContents="YES"/>
@@ -627,6 +627,43 @@
                                 <binding destination="58" name="value" keyPath="values.MMTranslateCtrlClick" id="ZMh-R3-AYN"/>
                             </connections>
                         </button>
+                        <button id="8rY-bA-ZQt">
+                            <rect key="frame" x="189" y="26" width="224" height="18"/>
+                            <autoresizingMask key="autoresizingMask" flexibleMinY="YES"/>
+                            <buttonCell key="cell" type="check" title="Disable scroll wheel acceleration" bezelStyle="regularSquare" imagePosition="left" alignment="left" inset="2" id="fRx-Gy-P0M">
+                                <behavior key="behavior" changeContents="YES" doesNotDimImage="YES" lightByContents="YES"/>
+                                <font key="font" metaFont="system"/>
+                            </buttonCell>
+                            <connections>
+                                <binding destination="58" name="value" keyPath="values.MMMouseWheelDisbleAcceleration" id="899-jt-taC"/>
+                            </connections>
+                        </button>
+                        <textField focusRingType="none" verticalHuggingPriority="750" horizontalCompressionResistancePriority="250" id="SqW-DB-w7i">
+                            <rect key="frame" x="210" y="3" width="109" height="17"/>
+                            <autoresizingMask key="autoresizingMask" flexibleMinY="YES"/>
+                            <textFieldCell key="cell" sendsActionOnEndEditing="YES" alignment="left" title="Lines to scroll:" id="w03-Ox-2xg">
+                                <font key="font" metaFont="system"/>
+                                <color key="textColor" name="controlTextColor" catalog="System" colorSpace="catalog"/>
+                                <color key="backgroundColor" name="controlColor" catalog="System" colorSpace="catalog"/>
+                            </textFieldCell>
+                            <connections>
+                                <binding destination="58" name="enabled" keyPath="values.MMMouseWheelDisbleAcceleration" id="Mzw-pC-FbR"/>
+                            </connections>
+                        </textField>
+                        <textField focusRingType="none" verticalHuggingPriority="750" id="Zpw-eU-7d1">
+                            <rect key="frame" x="305" y="1" width="32" height="21"/>
+                            <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
+                            <textFieldCell key="cell" scrollable="YES" lineBreakMode="clipping" selectable="YES" editable="YES" sendsActionOnEndEditing="YES" state="on" borderStyle="bezel" drawsBackground="YES" id="Vwr-3s-VFd">
+                                <numberFormatter key="formatter" formatterBehavior="default10_4" numberStyle="decimal" formatWidth="-1" minimumIntegerDigits="1" maximumIntegerDigits="2000000000" maximumFractionDigits="3" id="NEj-vx-0Qo"/>
+                                <font key="font" metaFont="system"/>
+                                <color key="textColor" name="controlTextColor" catalog="System" colorSpace="catalog"/>
+                                <color key="backgroundColor" name="textBackgroundColor" catalog="System" colorSpace="catalog"/>
+                            </textFieldCell>
+                            <connections>
+                                <binding destination="58" name="enabled" keyPath="values.MMMouseWheelDisbleAcceleration" id="i3X-ti-Cv8"/>
+                                <binding destination="58" name="value" keyPath="values.MMMouseWheelNumLines" id="ecJ-lb-ghs"/>
+                            </connections>
+                        </textField>
                     </subviews>
                 </customView>
                 <customView id="aUx-jX-mJJ" userLabel="Scrolling">

src/MacVim/MMAppController.m

@@ -217,6 +217,9 @@ + (void)registerDefaults
         [NSNumber numberWithBool:YES],    MMUseInlineImKey,
 #endif // INCLUDE_OLD_IM_CODE
         [NSNumber numberWithBool:NO],     MMSuppressTerminationAlertKey,
+        [NSNumber numberWithBool:NO],     MMMouseWheelDisableAccelerationKey,
+        [NSNumber numberWithInt:1],       MMMouseWheelMinLinesKey,
+        [NSNumber numberWithInt:3],       MMMouseWheelNumLinesKey,
         [NSNumber numberWithBool:YES],    MMNativeFullScreenKey,
         [NSNumber numberWithDouble:0.0],  MMFullScreenFadeTimeKey,
         [NSNumber numberWithBool:NO],     MMNonNativeFullScreenShowMenuKey,

src/MacVim/MMTextViewHelper.m

@@ -312,15 +312,15 @@ - (void)doCommandBySelector:(SEL)sel
     else interpretKeyEventsSwallowedKey = NO;
 }
 
-- (void)scrollWheel:(NSEvent *)event
+- (void)calcScrollWheelDeltas:(NSEvent *)event x:(float *)x y:(float *)y eventFlags:(NSEventModifierFlags*)eventFlags
 {
     float dx = 0;
     float dy = 0;
 
-#if MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_X_VERSION_10_7
+    NSUserDefaults *ud = [NSUserDefaults standardUserDefaults];
+
     if ([event hasPreciseScrollingDeltas]) {
         const NSEventPhase phase = event.phase;
-        NSUserDefaults *ud = [NSUserDefaults standardUserDefaults];
 
         CGFloat eventScrollingDeltaX = event.scrollingDeltaX;
         CGFloat eventScrollingDeltaY = event.scrollingDeltaY;
@@ -366,12 +366,40 @@ - (void)scrollWheel:(NSEvent *)event
         scrollingDeltaY = 0;
         dx = [event scrollingDeltaX];
         dy = [event scrollingDeltaY];
+
+        if ([ud boolForKey:MMMouseWheelDisableAccelerationKey]) {
+            // Use scroll wheel as discrete steps as macOS acceleration often
+            // leads to unintuitive results.
+            NSInteger numLines = [ud integerForKey:MMMouseWheelNumLinesKey];
+            dx = dx == 0 ? 0 : (dx > 0 ? numLines : -numLines);
+            dy = dy == 0 ? 0 : (dy > 0 ? numLines : -numLines);
+        } else {
+            // Use the default OS acceleration, but we still want to round up
+            // the delta to at least 1 (configurable) as otherwise it's
+            // frustrating to use as MacVim fails to scroll even one line.
+            NSInteger minScrollLines = [ud integerForKey:MMMouseWheelMinLinesKey];
+            dx = dx == 0 ? 0 : (fabs(dx) > minScrollLines ? dx : (dx > 0 ? minScrollLines : -minScrollLines));
+            dy = dy == 0 ? 0 : (fabs(dy) > minScrollLines ? dy : (dy > 0 ? minScrollLines : -minScrollLines));
+        }
+
+        if ((*eventFlags & NSEventModifierFlagShift) && dx != 0 && dy == 0) {
+            // A shift-scroll in macOS converts a normal Y to X-axis scroll.
+            // There is no proper API to query this so this is just done by
+            // heuristics. We need to remove the shift flag, or Vim would see
+            // this as a <S-ScrollWheelRight> which is not what we want.
+            *eventFlags = *eventFlags & (~NSEventModifierFlagShift);
+        }
     }
-#else
-    dx = [event deltaX];
-    dy = [event deltaY];
-#endif
 
+    *x = dx;
+    *y = dy;
+}
+
+- (void)scrollWheel:(NSEvent *)event
+{
+    NSEventModifierFlags eventFlags = event.modifierFlags;
+    float dx = 0, dy = 0;
+    [self calcScrollWheelDeltas:event x:&dx y:&dy eventFlags:&eventFlags];
     if (dx == 0 && dy == 0)
         return;
 
@@ -386,7 +414,7 @@ - (void)scrollWheel:(NSEvent *)event
     int row, col;
     NSPoint pt = [textView convertPoint:[event locationInWindow] fromView:nil];
     if ([textView convertPoint:pt toRow:&row column:&col]) {
-        unsigned flags = (unsigned)[event modifierFlags];
+        unsigned flags = (unsigned)eventFlags;
         NSMutableData *data = [NSMutableData data];
 
         [data appendBytes:&row length:sizeof(int)];

src/MacVim/Miscellaneous.h

@@ -61,6 +61,9 @@ extern NSString *MMUseInlineImKey;
 extern NSString *MMSuppressTerminationAlertKey;
 extern NSString *MMNativeFullScreenKey;
 extern NSString *MMUseMouseTimeKey;
+extern NSString *MMMouseWheelDisableAccelerationKey;    ///< Disable native macOS mouse scroll wheel acceleration
+extern NSString *MMMouseWheelMinLinesKey;   ///< Minimum scroll delta for mouse scroll wheel, only when acceleration is on
+extern NSString *MMMouseWheelNumLinesKey;   ///< Number of lines to scroll using mouse scroll wheel, only when acceleration is off
 extern NSString *MMFullScreenFadeTimeKey;
 extern NSString *MMNonNativeFullScreenShowMenuKey;
 extern NSString *MMNonNativeFullScreenSafeAreaBehaviorKey;
@@ -69,7 +72,7 @@ extern NSString *MMCmdLineAlignBottomKey;
 extern NSString *MMRendererClipToRowKey;
 extern NSString *MMAllowForceClickLookUpKey;
 extern NSString *MMUpdaterPrereleaseChannelKey;
-extern NSString *MMLastUsedBundleVersionKey;    // The last used version of MacVim before this launch
+extern NSString *MMLastUsedBundleVersionKey;    ///< The last used version of MacVim before this launch
 extern NSString *MMShowWhatsNewOnStartupKey;
 extern NSString *MMScrollOneDirectionOnlyKey;
 

src/MacVim/Miscellaneous.m

@@ -57,6 +57,9 @@
 NSString *MMSuppressTerminationAlertKey   = @"MMSuppressTerminationAlert";
 NSString *MMNativeFullScreenKey           = @"MMNativeFullScreen";
 NSString *MMUseMouseTimeKey               = @"MMUseMouseTime";
+NSString *MMMouseWheelDisableAccelerationKey    = @"MMMouseWheelDisbleAcceleration";
+NSString *MMMouseWheelMinLinesKey         = @"MMMouseWheelMinLines";
+NSString *MMMouseWheelNumLinesKey         = @"MMMouseWheelNumLines";
 NSString *MMFullScreenFadeTimeKey         = @"MMFullScreenFadeTime";
 NSString *MMNonNativeFullScreenShowMenuKey          = @"MMNonNativeFullScreenShowMenu";
 NSString *MMNonNativeFullScreenSafeAreaBehaviorKey  = @"MMNonNativeFullScreenSafeAreaBehavior";