Mobile: Working on scroll bounce behavior

6 files changed, 101 insertions, 18 deletions

diff --git a/src/app.h b/src/app.h
index 4eae7afd..9f3754cc 100644
--- a/src/app.h
+++ b/src/app.h
@@ -61,6 +61,7 @@ enum iUserEventCode {
        sending SDL_MOUSEBUTTONDOWN would be premature: we don't know how long the tap will
        take, it could turn into a tap-and-hold for example. */
     widgetTapBegins_UserEventCode = 4,
+    widgetTouchEnds_UserEventCode = 5, /* finger lifted, but momentum may continue */
 };
 
 const iString *execPath_App     (void);
diff --git a/src/ui/documentwidget.c b/src/ui/documentwidget.c
index c3728b75..87c724de 100644
--- a/src/ui/documentwidget.c
+++ b/src/ui/documentwidget.c
@@ -287,6 +287,7 @@ struct Impl_DocumentWidget {
     iDrawBufs *    drawBufs; /* dynamic state for drawing */
     iTranslation * translation;
     iWidget *      phoneToolbar;
+    int            overscroll;
     int            pinchZoomInitial;
     int            pinchZoomPosted;
 };
@@ -299,8 +300,9 @@ void init_DocumentWidget(iDocumentWidget *d) {
     setId_Widget(w, "document000");
     setFlags_Widget(w, hover_WidgetFlag, iTrue);
     init_PersistentDocumentState(&d->mod);
-    d->flags = 0;
-    d->phoneToolbar = NULL;
+    d->flags           = 0;
+    d->phoneToolbar    = NULL;
+    d->overscroll      = deviceType_App() != desktop_AppDeviceType ? 50 * gap_UI : 0;
     iZap(d->certExpiry);
     d->certFingerprint  = new_Block(0);
     d->certFlags        = 0;
@@ -1255,6 +1257,20 @@ static void refreshWhileScrolling_DocumentWidget_(iAny *ptr) {
     }
 }
 
+static int overscroll_DocumentWidget_(const iDocumentWidget *d) {
+    if (d->overscroll) {
+        const int y = value_Anim(&d->scrollY);
+        if (y <= 0) {
+            return y;
+        }
+        const int scrollMax = scrollMax_DocumentWidget_(d);
+        if (y >= scrollMax) {
+            return y - scrollMax;
+        }
+    }
+    return 0;
+}
+
 static void smoothScroll_DocumentWidget_(iDocumentWidget *d, int offset, int duration) {
     /* Get rid of link numbers when scrolling. */
     if (offset && d->flags & showLinkNumbers_DocumentWidgetFlag) {
@@ -1267,19 +1283,19 @@ static void smoothScroll_DocumentWidget_(iDocumentWidget *d, int offset, int dur
             showToolbars_Window(get_Window(), offset < 0);
         }
     }
+#if !defined (iPlatformMobile)
     if (!prefs_App()->smoothScrolling) {
         duration = 0; /* always instant */
     }
+#endif
     int destY = targetValue_Anim(&d->scrollY) + offset;
-    if (destY < 0) {
-        destY = 0;
-        stopWidgetMomentum_Touch(as_Widget(d));
+    if (destY < -2 * d->overscroll) {
+        destY = -2 * d->overscroll;
     }
     const int scrollMax = scrollMax_DocumentWidget_(d);
     if (scrollMax > 0) {
-        if (destY >= scrollMax) {
-            stopWidgetMomentum_Touch(as_Widget(d));
-            destY = scrollMax;
+        if (destY >= scrollMax + 2 * d->overscroll) {
+            destY = scrollMax + 2 * d->overscroll;
         }
     }
     else {
@@ -1291,6 +1307,18 @@ static void smoothScroll_DocumentWidget_(iDocumentWidget *d, int offset, int dur
     else {
         setValue_Anim(&d->scrollY, destY, 0);
     }
+    if (d->overscroll && widgetMode_Touch(as_Widget(d)) == momentum_WidgetTouchMode) {
+        const int osDelta = overscroll_DocumentWidget_(d);
+        if (osDelta) {
+            const float remaining = stopWidgetMomentum_Touch(as_Widget(d));
+            duration = iMini(1000, 50 * sqrt(remaining / gap_UI));
+            setValue_Anim(&d->scrollY, osDelta < 0 ? 0 : scrollMax, duration);
+            d->scrollY.flags = bounce_AnimFlag | easeOut_AnimFlag | softer_AnimFlag;
+            printf("remaining: %f  dur: %d\n", remaining, duration);
+            d->scrollY.bounce = (osDelta < 0 ? -1 : 1) *
+                iMini(10 * d->overscroll, remaining * remaining * 0.00005f);
+        }
+    }
     updateVisible_DocumentWidget_(d);
     refresh_Widget(as_Widget(d));
     if (duration > 0) {
@@ -2594,6 +2622,14 @@ static iBool processEvent_DocumentWidget_(iDocumentWidget *d, const SDL_Event *e
     if (isMetricsChange_UserEvent(ev)) {
         updateSize_DocumentWidget(d);
     }
+    else if (ev->type == SDL_USEREVENT && ev->user.code == widgetTouchEnds_UserEventCode) {
+        const int osDelta = overscroll_DocumentWidget_(d);
+        if (osDelta) {
+            smoothScroll_DocumentWidget_(d, -osDelta, 100 * sqrt(iAbs(osDelta) / gap_UI));
+            d->scrollY.flags = easeOut_AnimFlag | muchSofter_AnimFlag;
+        }
+        return iTrue;
+    }
     else if (ev->type == SDL_USEREVENT && ev->user.code == command_UserEventCode) {
         if (!handleCommand_DocumentWidget_(d, command_UserEvent(ev))) {
             /* Base class commands. */
@@ -3913,7 +3949,7 @@ static void draw_DocumentWidget_(const iDocumentWidget *d) {
     };
     render_DocumentWidget_(d, &ctx, iFalse /* just the mandatory parts */);
     setClip_Paint(&ctx.paint, bounds);
-    const int yTop = docBounds.pos.y - value_Anim(&d->scrollY);
+    int yTop = docBounds.pos.y - value_Anim(&d->scrollY) + overscroll_DocumentWidget_(d) * 0.667f;
     draw_VisBuf(d->visBuf, init_I2(bounds.pos.x, yTop), ySpan_Rect(bounds));
     /* Text markers. */
     const iBool isTouchSelecting = (flags_Widget(w) & touchDrag_WidgetFlag) != 0;
diff --git a/src/ui/touch.c b/src/ui/touch.c
index 834fe4f8..22f22f9b 100644
--- a/src/ui/touch.c
+++ b/src/ui/touch.c
@@ -686,6 +686,9 @@ iBool processEvent_Touch(const SDL_Event *ev) {
                     //dispatchMotion_Touch_(touch->startPos, 0);
                 }
                 else {
+                    if (touch->affinity) {
+                        dispatchNotification_Touch_(touch, widgetTouchEnds_UserEventCode);
+                    }
                     dispatchButtonUp_Touch_(pos);
                     setHover_Widget(NULL);
                 }
@@ -696,14 +699,34 @@ iBool processEvent_Touch(const SDL_Event *ev) {
     return iTrue;
 }
 
-void stopWidgetMomentum_Touch(iWidget *widget) {
+float stopWidgetMomentum_Touch(const iWidget *widget) {
     iTouchState *d = touchState_();
+    float remaining = 0.0f;
     iForEach(Array, i, d->moms) {
         iMomentum *mom = i.value;
         if (mom->affinity == widget) {
+            remaining = length_F3(mom->velocity);
             remove_ArrayIterator(&i);
         }
     }
+    return remaining;
+}
+
+enum iWidgetTouchMode widgetMode_Touch(const iWidget *widget) {
+    iTouchState *d = touchState_();
+    iConstForEach(Array, i, d->touches) {
+        const iTouch *touch = i.value;
+        if (touch->affinity == widget) {
+            return touch_WidgetTouchMode;
+        }
+    }
+    iConstForEach(Array, j, d->moms) {
+        const iMomentum *mom = j.value;
+        if (mom->affinity == widget) {
+            return momentum_WidgetTouchMode;
+        }
+    }
+    return none_WidgetTouchMode;
 }
 
 void widgetDestroyed_Touch(iWidget *widget) {
diff --git a/src/ui/touch.h b/src/ui/touch.h
index 0a24248b..1a6fb350 100644
--- a/src/ui/touch.h
+++ b/src/ui/touch.h
@@ -27,10 +27,18 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */
 
 iDeclareType(Widget)
 
+enum iWidgetTouchMode {
+    none_WidgetTouchMode,
+    touch_WidgetTouchMode,
+    momentum_WidgetTouchMode,
+};
+
 iBool   processEvent_Touch      (const SDL_Event *);
 void    update_Touch            (void);
-void    stopWidgetMomentum_Touch(iWidget *widget);
-void    widgetDestroyed_Touch   (iWidget *widget);
+
+float                   stopWidgetMomentum_Touch    (const iWidget *widget);
+enum iWidgetTouchMode   widgetMode_Touch            (const iWidget *widget);
+void                    widgetDestroyed_Touch       (iWidget *widget);
 
 iInt2   latestPosition_Touch    (void); /* valid during processing of current event */
 size_t  numFingers_Touch        (void);
diff --git a/src/ui/util.c b/src/ui/util.c
index 8e808bd2..877ec7c1 100644
--- a/src/ui/util.c
+++ b/src/ui/util.c
@@ -246,6 +246,7 @@ iBool isFinished_Anim(const iAnim *d) {
 void init_Anim(iAnim *d, float value) {
     d->due = d->when = SDL_GetTicks();
     d->from = d->to = value;
+    d->bounce = 0.0f;
     d->flags = 0;
 }
 
@@ -276,20 +277,29 @@ static float valueAt_Anim_(const iAnim *d, const uint32_t now) {
         return d->from;
     }
     float t = pos_Anim_(d, now);
-    const iBool isSoft = (d->flags & softer_AnimFlag) != 0;
+    const iBool isSoft     = (d->flags & softer_AnimFlag) != 0;
+    const iBool isVerySoft = (d->flags & muchSofter_AnimFlag) != 0;
     if ((d->flags & easeBoth_AnimFlag) == easeBoth_AnimFlag) {
         t = easeBoth_(t);
         if (isSoft) t = easeBoth_(t);
+        if (isVerySoft) t = easeBoth_(easeBoth_(t));
     }
     else if (d->flags & easeIn_AnimFlag) {
         t = easeIn_(t);
         if (isSoft) t = easeIn_(t);
+        if (isVerySoft) t = easeIn_(easeIn_(t));
     }
     else if (d->flags & easeOut_AnimFlag) {
         t = easeOut_(t);
         if (isSoft) t = easeOut_(t);
+        if (isVerySoft) t = easeOut_(easeOut_(t));
     }
-    return d->from * (1.0f - t) + d->to * t;
+    float value = d->from * (1.0f - t) + d->to * t;
+    if (d->flags & bounce_AnimFlag) {
+        t = (1.0f - easeOut_(easeOut_(t))) * easeOut_(t);
+        value += d->bounce * t;
+    }
+    return value;
 }
 
 void setValue_Anim(iAnim *d, float to, uint32_t span) {
@@ -304,6 +314,7 @@ void setValue_Anim(iAnim *d, float to, uint32_t span) {
         d->when = now;
         d->due  = now + span;
     }
+    d->bounce = 0;
 }
 
 void setValueSpeed_Anim(iAnim *d, float to, float unitsPerSecond) {
@@ -316,6 +327,7 @@ void setValueSpeed_Anim(iAnim *d, float to, float unitsPerSecond) {
         d->to                = to;
         d->when              = now;
         d->due               = d->when + span;
+        d->bounce            = 0;
     }
 }
 
@@ -333,9 +345,10 @@ void setValueEased_Anim(iAnim *d, float to, uint32_t span) {
         d->from  = valueAt_Anim_(d, now);
         d->flags = easeOut_AnimFlag;
     }
-    d->to   = to;
-    d->when = now;
-    d->due  = now + span;
+    d->to     = to;
+    d->when   = now;
+    d->due    = now + span;
+    d->bounce = 0;
 }
 
 void setFlags_Anim(iAnim *d, int flags, iBool set) {
diff --git a/src/ui/util.h b/src/ui/util.h
index d39a00fa..191b8a87 100644
--- a/src/ui/util.h
+++ b/src/ui/util.h
@@ -105,10 +105,12 @@ enum iAnimFlag {
     easeOut_AnimFlag    = iBit(3),
     easeBoth_AnimFlag   = easeIn_AnimFlag | easeOut_AnimFlag,
     softer_AnimFlag     = iBit(4),
+    muchSofter_AnimFlag = iBit(5),
+    bounce_AnimFlag     = iBit(6),
 };
 
 struct Impl_Anim {
-    float    from, to;
+    float    from, to, bounce;
     uint32_t when, due;
     int      flags;
 };