From 63dc07ddbecfdf0be7c0bd98c53e492628dda98b Mon Sep 17 00:00:00 2001
From: Jaakko Keränen <jaakko.keranen@iki.fi>
Date: Fri, 19 Feb 2021 10:50:41 +0200
Subject: Touch: Scrollbars can be dragged via touch

Widgets can be flagged as being touch-draggable, which makes them receive finger down/motion/up events directly, and no momentum scrolling is applied.
---
 src/ui/inputwidget.c  |  2 +-
 src/ui/scrollwidget.c |  2 +-
 src/ui/touch.c        | 41 ++++++++++++++++++++++++++++++++++++++++-
 src/ui/widget.h       |  1 +
 4 files changed, 43 insertions(+), 3 deletions(-)

(limited to 'src')

diff --git a/src/ui/inputwidget.c b/src/ui/inputwidget.c
index b51bd3ef..2f0fa064 100644
--- a/src/ui/inputwidget.c
+++ b/src/ui/inputwidget.c
@@ -108,7 +108,7 @@ static void showCursor_InputWidget_(iInputWidget *d) {
 void init_InputWidget(iInputWidget *d, size_t maxLen) {
     iWidget *w = &d->widget;
     init_Widget(w);
-    setFlags_Widget(w, focusable_WidgetFlag | hover_WidgetFlag, iTrue);
+    setFlags_Widget(w, focusable_WidgetFlag | hover_WidgetFlag | touchDrag_WidgetFlag, iTrue);
     init_Array(&d->text, sizeof(iChar));
     init_Array(&d->oldText, sizeof(iChar));
     init_String(&d->hint);
diff --git a/src/ui/scrollwidget.c b/src/ui/scrollwidget.c
index 649d0575..34efba67 100644
--- a/src/ui/scrollwidget.c
+++ b/src/ui/scrollwidget.c
@@ -41,7 +41,7 @@ void init_ScrollWidget(iScrollWidget *d) {
     setId_Widget(w, "scroll");
     setFlags_Widget(w,
                     fixedWidth_WidgetFlag | resizeToParentHeight_WidgetFlag |
-                        moveToParentRightEdge_WidgetFlag,
+                        moveToParentRightEdge_WidgetFlag | touchDrag_WidgetFlag,
                     iTrue);
     w->rect.size.x = gap_UI * 3;
     init_Click(&d->click, d, SDL_BUTTON_LEFT);
diff --git a/src/ui/touch.c b/src/ui/touch.c
index dbb16bd5..9b47d0fe 100644
--- a/src/ui/touch.c
+++ b/src/ui/touch.c
@@ -212,9 +212,23 @@ iBool processEvent_Touch(const SDL_Event *ev) {
             edge = right_TouchEdge;
         }
         iWidget *aff = hitChild_Widget(window->root, init_I2(iRound(x), iRound(y_F3(pos))));
+        if (flags_Widget(aff) & touchDrag_WidgetFlag) {
+            dispatchEvent_Widget(window->root, (SDL_Event *) &(SDL_MouseButtonEvent){
+                .type = SDL_MOUSEBUTTONDOWN,
+                .timestamp = fing->timestamp,
+                .clicks = 1,
+                .state = SDL_PRESSED,
+                .which = SDL_TOUCH_MOUSEID,
+                .button = SDL_BUTTON_LEFT,
+                .x = x_F3(pos),
+                .y = y_F3(pos)
+            });
+            edge = none_TouchEdge;
+        }
         pushBack_Array(d->touches, &(iTouch){
             .id = fing->fingerId,
             .affinity = aff,
+            .hasMoved = (flags_Widget(aff) & touchDrag_WidgetFlag) != 0,
             .edge = edge,
             .startTime = nowTime,
             .startPos = pos,
@@ -223,7 +237,7 @@ iBool processEvent_Touch(const SDL_Event *ev) {
         /* Some widgets rely on hover state. */
         dispatchEvent_Widget(window->root, (SDL_Event *) &(SDL_MouseMotionEvent){
             .type = SDL_MOUSEMOTION,
-            .timestamp = SDL_GetTicks(),
+            .timestamp = fing->timestamp,
             .which = SDL_TOUCH_MOUSEID,
             .x = x_F3(pos),
             .y = y_F3(pos)
@@ -233,6 +247,17 @@ iBool processEvent_Touch(const SDL_Event *ev) {
     else if (ev->type == SDL_FINGERMOTION) {
         iTouch *touch = find_TouchState_(d, fing->fingerId);
         if (touch && touch->affinity) {
+            if (flags_Widget(touch->affinity) & touchDrag_WidgetFlag) {
+                dispatchEvent_Widget(window->root, (SDL_Event *) &(SDL_MouseMotionEvent){
+                    .type = SDL_MOUSEMOTION,
+                    .timestamp = fing->timestamp,
+                    .which = SDL_TOUCH_MOUSEID,
+                    .state = SDL_BUTTON_LMASK,
+                    .x = x_F3(pos),
+                    .y = y_F3(pos)
+                });
+                return iTrue;
+            }
             /* Update touch position. */
             pushPos_Touch_(touch, pos, nowTime);
             const iFloat3 amount = add_F3(touch->remainder,
@@ -278,6 +303,20 @@ iBool processEvent_Touch(const SDL_Event *ev) {
             if (touch->id != fing->fingerId) {
                 continue;
             }
+            if (flags_Widget(touch->affinity) & touchDrag_WidgetFlag) {
+                dispatchEvent_Widget(window->root, (SDL_Event *) &(SDL_MouseButtonEvent){
+                    .type = SDL_MOUSEBUTTONUP,
+                    .timestamp = fing->timestamp,
+                    .clicks = 1,
+                    .state = SDL_RELEASED,
+                    .which = SDL_TOUCH_MOUSEID,
+                    .button = SDL_BUTTON_LEFT,
+                    .x = x_F3(pos),
+                    .y = y_F3(pos)
+                });
+                remove_ArrayIterator(&i);
+                continue;
+            }
             /* Edge swipes do not generate momentum. */
             const uint32_t duration = nowTime - touch->startTime;
             const iFloat3 gestureVector = sub_F3(pos, touch->startPos);
diff --git a/src/ui/widget.h b/src/ui/widget.h
index a9756793..0b7a76e1 100644
--- a/src/ui/widget.h
+++ b/src/ui/widget.h
@@ -92,6 +92,7 @@ enum iWidgetFlag {
 #define overflowScrollable_WidgetFlag       iBit64(38)
 #define focusRoot_WidgetFlag                iBit64(39)
 #define unhittable_WidgetFlag               iBit64(40)
+#define touchDrag_WidgetFlag                iBit64(41) /* touch event behavior: immediate drag */
 
 enum iWidgetAddPos {
     back_WidgetAddPos,
-- 
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