5 files changed, 23 insertions, 3 deletions

diff --git a/src/app.c b/src/app.c
index 37279391..a76e135b 100644
--- a/src/app.c
+++ b/src/app.c
@@ -180,6 +180,7 @@ static iString *serializePrefs_App_(const iApp *d) {
     appendFormat_String(str, "font.set arg:%d\n", d->prefs.font);
     appendFormat_String(str, "headingfont.set arg:%d\n", d->prefs.headingFont);
     appendFormat_String(str, "zoom.set arg:%d\n", d->prefs.zoomPercent);
+    appendFormat_String(str, "smoothscroll arg:%d\n", d->prefs.smoothScrolling);
     appendFormat_String(str, "linewidth.set arg:%d\n", d->prefs.lineWidth);
     appendFormat_String(str, "prefs.biglede.changed arg:%d\n", d->prefs.bigFirstParagraph);
     appendFormat_String(str, "prefs.sideicon.changed arg:%d\n", d->prefs.sideIcon);
@@ -735,6 +736,8 @@ static iBool handlePrefsCommands_(iWidget *d, const char *cmd) {
                          cstr_String(text_InputWidget(findChild_Widget(d, "prefs.downloads"))));
         postCommandf_App("window.retain arg:%d",
                          isSelected_Widget(findChild_Widget(d, "prefs.retainwindow")));
+        postCommandf_App("smoothscroll arg:%d",
+                         isSelected_Widget(findChild_Widget(d, "prefs.smoothscroll")));
         postCommandf_App("ostheme arg:%d",
                          isSelected_Widget(findChild_Widget(d, "prefs.ostheme")));
         postCommandf_App("proxy.http address:%s",
@@ -942,6 +945,10 @@ iBool handleCommand_App(const char *cmd) {
         postCommand_App("window.unfreeze");
         return iTrue;
     }
+    else if (equal_Command(cmd, "smoothscroll")) {
+        d->prefs.smoothScrolling = arg_Command(cmd);
+        return iTrue;
+    }
     else if (equal_Command(cmd, "forcewrap.toggle")) {
         d->prefs.forceLineWrap = !d->prefs.forceLineWrap;
         updateSize_DocumentWidget(document_App());
@@ -1119,6 +1126,7 @@ iBool handleCommand_App(const char *cmd) {
         updatePrefsThemeButtons_(dlg);
         setText_InputWidget(findChild_Widget(dlg, "prefs.downloads"), &d->prefs.downloadDir);
         setToggle_Widget(findChild_Widget(dlg, "prefs.hoveroutline"), d->prefs.hoverOutline);
+        setToggle_Widget(findChild_Widget(dlg, "prefs.smoothscroll"), d->prefs.smoothScrolling);
         setToggle_Widget(findChild_Widget(dlg, "prefs.ostheme"), d->prefs.useSystemTheme);
         setToggle_Widget(findChild_Widget(dlg, "prefs.retainwindow"), d->prefs.retainWindowSize);
         setText_InputWidget(findChild_Widget(dlg, "prefs.uiscale"),
diff --git a/src/prefs.c b/src/prefs.c
index 8d1dd8fe..815dac52 100644
--- a/src/prefs.c
+++ b/src/prefs.c
@@ -28,6 +28,7 @@ void init_Prefs(iPrefs *d) {
     d->useSystemTheme    = iTrue;
     d->retainWindowSize  = iTrue;
     d->zoomPercent       = 100;
+    d->smoothScrolling   = iTrue;
     d->forceLineWrap     = iFalse;
     d->quoteIcon         = iTrue;
     d->font              = nunito_TextFont;
diff --git a/src/prefs.h b/src/prefs.h
index eadfea64..bf642600 100644
--- a/src/prefs.h
+++ b/src/prefs.h
@@ -35,8 +35,9 @@ iDeclareType(Prefs)
 struct Impl_Prefs {
     int dialogTab;
     iBool retainWindowSize;
-    float uiScale;    
+    float uiScale;
     int zoomPercent;
+    iBool smoothScrolling;
     iBool useSystemTheme;
     enum iColorTheme theme;
     iString gopherProxy;
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:")));