Added an option to disable smooth scrolling

IssueID #27

2 files changed, 12 insertions, 2 deletions

diff --git a/src/ui/documentwidget.c b/src/ui/documentwidget.c
index 13f21df6..f1506fc3 100644
--- a/src/ui/documentwidget.c
+++ b/src/ui/documentwidget.c
@@ -947,6 +947,9 @@ static void refreshWhileScrolling_DocumentWidget_(iAny *ptr) {
 }
 
 static void smoothScroll_DocumentWidget_(iDocumentWidget *d, int offset, int duration) {
+    if (!prefs_App()->smoothScrolling) {
+        duration = 0; /* always instant */
+    }
     int destY = targetValue_Anim(&d->scrollY) + offset;
     if (destY < 0) {
         destY = 0;
@@ -958,7 +961,12 @@ static void smoothScroll_DocumentWidget_(iDocumentWidget *d, int offset, int dur
     else {
         destY = 0;
     }
-    setValueEased_Anim(&d->scrollY, destY, duration);
+    if (duration) {
+        setValueEased_Anim(&d->scrollY, destY, duration);
+    }
+    else {
+        setValue_Anim(&d->scrollY, destY, 0);
+    }
     updateVisible_DocumentWidget_(d);
     refresh_Widget(as_Widget(d));
     if (duration > 0) {
diff --git a/src/ui/util.c b/src/ui/util.c
index ceab01b8..e65e089d 100644
--- a/src/ui/util.c
+++ b/src/ui/util.c
@@ -188,7 +188,7 @@ static float valueAt_Anim_(const iAnim *d, const uint32_t now) {
 void setValue_Anim(iAnim *d, float to, uint32_t span) {
     if (span == 0) {
         d->from = d->to = to;
-        d->when = d->due = SDL_GetTicks();
+        d->when = d->due = frameTime_Window(get_Window()); /* effectively in the past */
     }
     else if (fabsf(to - d->to) > 0.00001f) {
         const uint32_t now = SDL_GetTicks();
@@ -997,6 +997,8 @@ iWidget *makePreferences_Widget(void) {
         setId_Widget(addChild_Widget(values, iClob(new_InputWidget(0))), "prefs.downloads");
         addChild_Widget(headings, iClob(makeHeading_Widget("Outline on scrollbar:")));
         addChild_Widget(values, iClob(makeToggle_Widget("prefs.hoveroutline")));
+        addChild_Widget(headings, iClob(makeHeading_Widget("Smooth scrolling:")));
+        addChild_Widget(values, iClob(makeToggle_Widget("prefs.smoothscroll")));
         makeTwoColumnHeading_("WINDOW", headings, values);
 #if defined (iPlatformApple) || defined (iPlatformMSys)
         addChild_Widget(headings, iClob(makeHeading_Widget("Use system theme:")));