Processing per-pixel scroll events

Do platform-specific processing of scroll events up front so widgets can support both types of scrolls everywhere.

IssueID #166

6 files changed, 84 insertions, 59 deletions

diff --git a/src/app.c b/src/app.c
index ada142f0..6a3dc00b 100644
--- a/src/app.c
+++ b/src/app.c
@@ -901,14 +901,40 @@ void processEvents_App(enum iAppEventMode eventMode) {
                 d->isIdling = iFalse;
 #endif
                 gotEvents = iTrue;
-                /* Keyboard modifier mapping. */ {
-                    if (ev.type == SDL_KEYDOWN || ev.type == SDL_KEYUP) {
-                        /* Track Caps Lock state as a modifier. */
-                        if (ev.key.keysym.sym == SDLK_CAPSLOCK) {
-                            setCapsLockDown_Keys(ev.key.state == SDL_PRESSED);
+                /* Keyboard modifier mapping. */
+                if (ev.type == SDL_KEYDOWN || ev.type == SDL_KEYUP) {
+                    /* Track Caps Lock state as a modifier. */
+                    if (ev.key.keysym.sym == SDLK_CAPSLOCK) {
+                        setCapsLockDown_Keys(ev.key.state == SDL_PRESSED);
+                    }
+                    ev.key.keysym.mod = mapMods_Keys(ev.key.keysym.mod & ~KMOD_CAPS);
+                }
+                /* Scroll events may be per-pixel or mouse wheel steps. */
+                if (ev.type == SDL_MOUSEWHEEL) {
+#if defined (iPlatformAppleDesktop)
+                    /* On macOS, we handle both trackpad and mouse events. We expect SDL to identify
+                       which device is sending the event. */
+                    if (ev.wheel.which == 0) {
+                        /* Trackpad with precise scrolling w/inertia (points). */
+                        setPerPixel_MouseWheelEvent(&ev.wheel, iTrue);
+                        ev.wheel.x *= -d->window->pixelRatio;
+                        ev.wheel.y *= d->window->pixelRatio;
+                        /* Only scroll on one axis at a time. */
+                        if (iAbs(ev.wheel.x) > iAbs(ev.wheel.y)) {
+                            ev.wheel.y = 0;
+                        }
+                        else {
+                            ev.wheel.x = 0;
                         }
-                        ev.key.keysym.mod = mapMods_Keys(ev.key.keysym.mod & ~KMOD_CAPS);
                     }
+                    else {
+                        /* Disregard wheel acceleration applied by the OS. */
+                        ev.wheel.y = iSign(ev.wheel.y);
+                    }
+#endif
+#if defined (iPlatformMsys)
+//                    ev.wheel.x = -ev.wheel.x;
+#endif
                 }
                 iBool wasUsed = processEvent_Window(d->window, &ev);
                 if (!wasUsed) {
diff --git a/src/ui/documentwidget.c b/src/ui/documentwidget.c
index 9b412783..f3083207 100644
--- a/src/ui/documentwidget.c
+++ b/src/ui/documentwidget.c
@@ -2324,37 +2324,33 @@ static iBool processEvent_DocumentWidget_(iDocumentWidget *d, const SDL_Event *e
         /* TODO: Maybe clean this up a bit? Wheel events are used for scrolling
            but they are calculated differently based on device/mouse/trackpad. */
         const iInt2 mouseCoord = mouseCoord_Window(get_Window());
-#if defined (iPlatformApple)
-        /* On macOS, we handle both trackpad and mouse events. We expect SDL to identify
-           which device is sending the event. */
-        if (ev->wheel.which == 0) { /* Trackpad with precise scrolling w/inertia. */
+        if (isPerPixel_MouseWheelEvent(&ev->wheel)) {
             stop_Anim(&d->scrollY);
             iInt2 wheel = init_I2(ev->wheel.x, ev->wheel.y);
-#   if defined (iPlatformAppleMobile)
-            wheel.x = -wheel.x;
-#   else
-            /* Wheel mounts are in points. */
-            mulfv_I2(&wheel, get_Window()->pixelRatio);
-            /* Only scroll on one axis at a time. */
-            if (iAbs(wheel.x) > iAbs(wheel.y)) {
-                wheel.y = 0;
-            }
-            else {
-                wheel.x = 0;
-            }
-#   endif
+//#   if defined (iPlatformAppleMobile)
+//            wheel.x = -wheel.x;
+//#   else
+//            /* Wheel mounts are in points. */
+//            mulfv_I2(&wheel, get_Window()->pixelRatio);
+//            /* Only scroll on one axis at a time. */
+//            if (iAbs(wheel.x) > iAbs(wheel.y)) {
+//                wheel.y = 0;
+//            }
+//            else {
+//                wheel.x = 0;
+//            }
+//#   endif
             scroll_DocumentWidget_(d, -wheel.y);
-            scrollWideBlock_DocumentWidget_(d, mouseCoord, wheel.x, 0);
+            scrollWideBlock_DocumentWidget_(d, mouseCoord, -wheel.x, 0);
         }
-        else
-#endif
-        /* Traditional mouse wheel. */ {
-#if defined (iPlatformApple)
-            /* Disregard wheel acceleration applied by the OS. */
-            const int amount = iSign(ev->wheel.y);
-#else
+        else {
+            /* Traditional mouse wheel. */
+//#if defined (iPlatformApple)
+//            /* Disregard wheel acceleration applied by the OS. */
+//            const int amount = iSign(ev->wheel.y);
+//#else
             const int amount = ev->wheel.y;
-#endif
+//#endif
             if (keyMods_Sym(modState_Keys()) == KMOD_PRIMARY) {
                 postCommandf_App("zoom.delta arg:%d", amount > 0 ? 10 : -10);
                 return iTrue;
@@ -2365,13 +2361,8 @@ static iBool processEvent_DocumentWidget_(iDocumentWidget *d, const SDL_Event *e
                 smoothDuration_DocumentWidget_ *
                     /* accelerated speed for repeated wheelings */
                     (!isFinished_Anim(&d->scrollY) && pos_Anim(&d->scrollY) < 0.25f ? 0.5f : 1.0f));
-#if defined (iPlatformMsys)
-            const int horizStep = ev->wheel.x * 3;
-#else
-            const int horizStep = ev->wheel.x * -3;
-#endif
             scrollWideBlock_DocumentWidget_(
-                d, mouseCoord, horizStep * lineHeight_Text(paragraph_FontId), 167);
+                d, mouseCoord, -3 * ev->wheel.x * lineHeight_Text(paragraph_FontId), 167);
         }
         iChangeFlags(d->flags, noHoverWhileScrolling_DocumentWidgetFlag, iTrue);
         return iTrue;
diff --git a/src/ui/listwidget.c b/src/ui/listwidget.c
index e7b4fc22..237562ca 100644
--- a/src/ui/listwidget.c
+++ b/src/ui/listwidget.c
@@ -303,14 +303,9 @@ static iBool processEvent_ListWidget_(iListWidget *d, const SDL_Event *ev) {
     }
     if (ev->type == SDL_MOUSEWHEEL && isHover_Widget(w)) {
         int amount = -ev->wheel.y;
-#if defined (iPlatformApple)
-#   if defined (iPlatformAppleDesktop)
-        /* Momentum scrolling (in points). */
-        amount *= get_Window()->pixelRatio;
-#   endif
-#else
-        amount *= 3 * d->itemHeight;
-#endif
+        if (!isPerPixel_MouseWheelEvent(&ev->wheel)) {
+            amount *= 3 * d->itemHeight;
+        }
         scrollOffset_ListWidget(d, amount);
         return iTrue;
     }
diff --git a/src/ui/text.c b/src/ui/text.c
index f380b67b..d9ddf2b2 100644
--- a/src/ui/text.c
+++ b/src/ui/text.c
@@ -708,12 +708,13 @@ void rasterizeSomePendingGlyphs_Text(void) {
 }
 
 enum iRunMode {
-    measure_RunMode    = 0,
-    draw_RunMode       = 1,
-    modeMask_RunMode   = 0x00ff,
-    flagsMask_RunMode  = 0xff00,
-    noWrapFlag_RunMode = iBit(9),
-    visualFlag_RunMode = iBit(10), /* actual visible bounding box of the glyph, e.g., for icons */
+    measure_RunMode                 = 0,
+    draw_RunMode                    = 1,
+    modeMask_RunMode                = 0x00ff,
+    flagsMask_RunMode               = 0xff00,
+    noWrapFlag_RunMode              = iBit(9),
+    visualFlag_RunMode              = iBit(10), /* actual visible bounding box of the glyph,
+                                                   e.g., for icons */
     permanentColorFlag_RunMode      = iBit(11),
     alwaysVariableWidthFlag_RunMode = iBit(12),
 };
diff --git a/src/ui/touch.c b/src/ui/touch.c
index 136457a5..6201b4b6 100644
--- a/src/ui/touch.c
+++ b/src/ui/touch.c
@@ -205,15 +205,15 @@ static void update_TouchState_(void *ptr) {
                 mulvf_F3(&mom->velocity, momFriction);
                 addv_F3(&mom->accum, mulf_F3(mom->velocity, stepDurationMs / 1000.0f));
             }
-            const iInt2 points = initF3_I2(mom->accum);
-            if (points.x || points.y) {
-                subv_F3(&mom->accum, initI2_F3(points));
+            const iInt2 pixels = initF3_I2(mom->accum);
+            if (pixels.x || pixels.y) {
+                subv_F3(&mom->accum, initI2_F3(pixels));
                 dispatchEvent_Widget(mom->affinity, (SDL_Event *) &(SDL_MouseWheelEvent){
                     .type = SDL_MOUSEWHEEL,
                     .timestamp = nowTime,
-                    .which = 0, /* means "precise scrolling" in DocumentWidget */
-                    .x = points.x,
-                    .y = points.y
+                    .x = pixels.x,
+                    .y = pixels.y,
+                    .direction = perPixel_MouseWheelFlag
                 });
             }
             if (length_F3(mom->velocity) < minSpeed) {
@@ -405,9 +405,9 @@ iBool processEvent_Touch(const SDL_Event *ev) {
                 dispatchEvent_Widget(touch->affinity, (SDL_Event *) &(SDL_MouseWheelEvent){
                     .type = SDL_MOUSEWHEEL,
                     .timestamp = SDL_GetTicks(),
-                    .which = 0, /* means "precise scrolling" in DocumentWidget */
                     .x = pixels.x,
                     .y = pixels.y,
+                    .direction = perPixel_MouseWheelFlag
                 });
                 dispatchMotion_Touch_(zero_F3(), 0);
                 /* TODO: Keep increasing movement if the direction is the same. */
diff --git a/src/ui/util.h b/src/ui/util.h
index 122cbb97..7a66ebb3 100644
--- a/src/ui/util.h
+++ b/src/ui/util.h
@@ -43,6 +43,18 @@ iLocalDef iBool isMetricsChange_UserEvent(const SDL_Event *d) {
     return isCommand_UserEvent(d, "metrics.changed");
 }
 
+enum iMouseWheelFlag {
+    perPixel_MouseWheelFlag = iBit(9), /* e.g., trackpad or finger scroll; applied to `direction` */
+};
+
+/* Note: A future version of SDL may support per-pixel scrolling, but 2.0.x doesn't. */
+iLocalDef void setPerPixel_MouseWheelEvent(SDL_MouseWheelEvent *ev, iBool set) {
+    iChangeFlags(ev->direction, perPixel_MouseWheelFlag, set);
+}
+iLocalDef iBool isPerPixel_MouseWheelEvent(const SDL_MouseWheelEvent *ev) {
+    return (ev->direction & perPixel_MouseWheelFlag) != 0;
+}
+
 #if defined (iPlatformApple)
 #   define KMOD_PRIMARY     KMOD_GUI
 #   define KMOD_SECONDARY   KMOD_CTRL