Limit the timeline vertical separator pos in getter instead of setter

Fixed regression introduced in 7170762f08009cc69e7e8d81a29d7e2435a4eeed,
we must keep the original value so resizing the window doesn't reset
the value limiting it, or other strange situations where the value is
not saved correctly, e.g.:
https://community.aseprite.org/t/6107
https://community.aseprite.org/t/6097/6

src/app/ui/timeline/timeline.cpp

@@ -1523,7 +1523,6 @@ void Timeline::onResize(ui::ResizeEvent& ev)
 {
   gfx::Rect rc = ev.bounds();
   setBoundsQuietly(rc);
-  setSeparatorX(m_separator_x);
 
   gfx::Size sz = m_aniControls.sizeHint();
   m_aniControls.setBounds(
@@ -1531,7 +1530,7 @@ void Timeline::onResize(ui::ResizeEvent& ev)
       rc.x,
       rc.y+(visibleTagBands()-1)*oneTagHeight(),
       (!m_sprite || m_sprite->tags().empty() ? std::min(sz.w, rc.w):
-                                               std::min(sz.w, m_separator_x)),
+                                               std::min(sz.w, separatorX())),
       oneTagHeight()));
 
   updateScrollBars();
@@ -2628,7 +2627,7 @@ void Timeline::drawPaddings(ui::Graphics* g)
 gfx::Rect Timeline::getLayerHeadersBounds() const
 {
   gfx::Rect rc = clientBounds();
-  rc.w = m_separator_x;
+  rc.w = separatorX();
   int h = topHeight() + headerBoxHeight();
   rc.y += h;
   rc.h -= h;
@@ -2638,9 +2637,9 @@ gfx::Rect Timeline::getLayerHeadersBounds() const
 gfx::Rect Timeline::getFrameHeadersBounds() const
 {
   gfx::Rect rc = clientBounds();
-  rc.x += m_separator_x;
+  rc.x += separatorX();
   rc.y += topHeight();
-  rc.w -= m_separator_x;
+  rc.w -= separatorX();
   rc.h = headerBoxHeight();
   return rc;
 }
@@ -2667,8 +2666,8 @@ gfx::Rect Timeline::getOnionskinFramesBounds() const
 gfx::Rect Timeline::getCelsBounds() const
 {
   gfx::Rect rc = clientBounds();
-  rc.x += m_separator_x;
+  rc.x += separatorX();
-  rc.w -= m_separator_x;
+  rc.w -= separatorX();
   rc.y += headerBoxHeight() + topHeight();
   rc.h -= headerBoxHeight() + topHeight();
   return rc;
@@ -2688,8 +2687,8 @@ gfx::Rect Timeline::getPartBounds(const Hit& hit) const
       return gfx::Rect(bounds.x, bounds.y, bounds.w, y);
 
     case PART_SEPARATOR:
-      return gfx::Rect(bounds.x + m_separator_x, bounds.y + y,
+      return gfx::Rect(bounds.x + separatorX(), bounds.y + y,
-        m_separator_x + m_separator_w, bounds.h - y);
+                       separatorX() + m_separator_w, bounds.h - y);
 
     case PART_HEADER_EYE:
       return gfx::Rect(bounds.x + headerBoxWidth()*0, bounds.y + y,
@@ -2713,11 +2712,11 @@ gfx::Rect Timeline::getPartBounds(const Hit& hit) const
 
     case PART_HEADER_LAYER:
       return gfx::Rect(bounds.x + headerBoxWidth()*5, bounds.y + y,
-                       m_separator_x - headerBoxWidth()*5, headerBoxHeight());
+                       separatorX() - headerBoxWidth()*5, headerBoxHeight());
 
     case PART_HEADER_FRAME:
       return gfx::Rect(
-        bounds.x + m_separator_x + m_separator_w - 1
+        bounds.x + separatorX() + m_separator_w - 1
         + frameBoxWidth()*std::max(firstFrame(), hit.frame) - viewScroll().x,
         bounds.y + y, frameBoxWidth(), headerBoxHeight());
 
@@ -2725,7 +2724,7 @@ gfx::Rect Timeline::getPartBounds(const Hit& hit) const
       if (validLayer(hit.layer)) {
         return gfx::Rect(bounds.x,
           bounds.y + y + headerBoxHeight() + layerBoxHeight()*(lastLayer()-hit.layer) - viewScroll().y,
-          m_separator_x, layerBoxHeight());
+          separatorX(), layerBoxHeight());
       }
       break;
 
@@ -2758,14 +2757,14 @@ gfx::Rect Timeline::getPartBounds(const Hit& hit) const
         int x = headerBoxWidth()*3;
         return gfx::Rect(bounds.x + x,
           bounds.y + y + headerBoxHeight() + layerBoxHeight()*(lastLayer()-hit.layer) - viewScroll().y,
-          m_separator_x - x, layerBoxHeight());
+          separatorX() - x, layerBoxHeight());
       }
       break;
 
     case PART_CEL:
       if (validLayer(hit.layer) && hit.frame >= frame_t(0)) {
         return gfx::Rect(
-          bounds.x + m_separator_x + m_separator_w - 1 + frameBoxWidth()*hit.frame - viewScroll().x,
+          bounds.x + separatorX() + m_separator_w - 1 + frameBoxWidth()*hit.frame - viewScroll().x,
           bounds.y + y + headerBoxHeight() + layerBoxHeight()*(lastLayer()-hit.layer) - viewScroll().y,
           frameBoxWidth(), layerBoxHeight());
       }
@@ -2809,16 +2808,16 @@ gfx::Rect Timeline::getPartBounds(const Hit& hit) const
 
     case PART_TAGS:
       return gfx::Rect(
-        bounds.x + m_separator_x + m_separator_w - 1,
+        bounds.x + separatorX() + m_separator_w - 1,
         bounds.y,
-        bounds.w - m_separator_x - m_separator_w + 1, y);
+        bounds.w - separatorX() - m_separator_w + 1, y);
 
     case PART_TAG_BAND:
       return gfx::Rect(
-        bounds.x + m_separator_x + m_separator_w - 1,
+        bounds.x + separatorX() + m_separator_w - 1,
         bounds.y
         + (m_tagFocusBand < 0 ? oneTagHeight() * std::max(0, hit.band): 0),
-        bounds.w - m_separator_x - m_separator_w + 1,
+        bounds.w - separatorX() - m_separator_w + 1,
         oneTagHeight());
 
     case PART_TAG_SWITCH_BUTTONS: {
@@ -3059,7 +3058,7 @@ Timeline::Hit Timeline::hitTest(ui::Message* msg, const gfx::Point& mousePos)
         + scroll.y) / layerBoxHeight());
 
     hit.frame = frame_t((mousePos.x
-        - m_separator_x
+        - separatorX()
         - m_separator_w
         + scroll.x) / frameBoxWidth());
 
@@ -3088,8 +3087,8 @@ Timeline::Hit Timeline::hitTest(ui::Message* msg, const gfx::Point& mousePos)
       hit.part = PART_HEADER_ONIONSKIN_RANGE_RIGHT;
     }
     // Is the mouse on the separator.
-    else if (mousePos.x > m_separator_x-4
+    else if (mousePos.x > separatorX()-4
-          && mousePos.x <= m_separator_x)  {
+          && mousePos.x <= separatorX())  {
       hit.part = PART_SEPARATOR;
     }
     // Is the mouse on the frame tags area?
@@ -3164,7 +3163,7 @@ Timeline::Hit Timeline::hitTest(ui::Message* msg, const gfx::Point& mousePos)
     }
     // Is the mouse on the headers?
     else if (mousePos.y >= top && mousePos.y < top+headerBoxHeight()) {
-      if (mousePos.x < m_separator_x) {
+      if (mousePos.x < separatorX()) {
         if (getPartBounds(Hit(PART_HEADER_EYE)).contains(mousePos))
           hit.part = PART_HEADER_EYE;
         else if (getPartBounds(Hit(PART_HEADER_PADLOCK)).contains(mousePos))
@@ -3186,7 +3185,7 @@ Timeline::Hit Timeline::hitTest(ui::Message* msg, const gfx::Point& mousePos)
     else if (mousePos.y < top+headerBoxHeight())
       hit.part = PART_TOP;
     // Is the mouse on a layer's label?
-    else if (mousePos.x < m_separator_x) {
+    else if (mousePos.x < separatorX()) {
       if (getPartBounds(Hit(PART_ROW_EYE_ICON, hit.layer)).contains(mousePos))
         hit.part = PART_ROW_EYE_ICON;
       else if (getPartBounds(Hit(PART_ROW_PADLOCK_ICON, hit.layer)).contains(mousePos))
@@ -3242,7 +3241,7 @@ Timeline::Hit Timeline::hitTestCel(const gfx::Point& mousePos)
      + scroll.y) / layerBoxHeight());
 
   hit.frame = frame_t((mousePos.x
-                       - m_separator_x
+                       - separatorX()
                        - m_separator_w
                        + scroll.x) / frameBoxWidth());
 
@@ -4224,9 +4223,14 @@ void Timeline::setLayerCollapsedFlag(const layer_t l, const bool state)
   }
 }
 
+int Timeline::separatorX() const
+{
+  return base::clamp(m_separator_x, headerBoxWidth(), bounds().w-guiscale());
+}
+
 void Timeline::setSeparatorX(int newValue)
 {
-  m_separator_x = base::clamp(newValue, headerBoxWidth(), bounds().w-guiscale());
+  m_separator_x = std::max(0, newValue);
 }
 
 } // namespace app

src/app/ui/timeline/timeline.h

@@ -357,6 +357,7 @@ namespace app {
     void setLayerContinuousFlag(const layer_t layer, const bool state);
     void setLayerCollapsedFlag(const layer_t layer, const bool state);
 
+    int separatorX() const;
     void setSeparatorX(int newValue);
 
     ui::ScrollBar m_hbar;