DoubleSlider: Fixed a click on hovered tick, when object is height enough.

(layer step is less then 2px)
SPE-2421

src/slic3r/GUI/DoubleSliderForLayers.cpp

@@ -207,6 +207,7 @@ void DSForLayers::draw_ticks(const ImRect& slideable_region)
     };
 
     std::set<TickCode>::const_iterator tick_it = m_ticks.ticks.begin();
+    bool is_hovered_tick = false;
     while (tick_it != m_ticks.ticks.end())
     {
         float tick_pos = get_tick_pos(tick_it->tick);
@@ -221,11 +222,17 @@ void DSForLayers::draw_ticks(const ImRect& slideable_region)
                 m_focus = fiTick;
                 ImGuiPureWrap::tooltip(get_tooltip(tick_it->tick), ImGui::GetFontSize() * 20.f);
             }
+            is_hovered_tick = true;
+            m_ctrl.SetHoveredRegion(tick_hover_box);
+            if (m_ctrl.IsLClickOnHoveredPos())
+                m_ctrl.IsActiveHigherThumb() ? SetHigherPos(tick_it->tick) : SetLowerPos(tick_it->tick);
             break;
         }
         ++tick_it;
     }
-     
+    if (!is_hovered_tick)
+        m_ctrl.InvalidateHoveredRegion();
+
     auto active_tick_it = m_ticks.ticks.find(TickCode{ m_ctrl.GetActivePos() });
 
     tick_it = m_ticks.ticks.begin();

src/slic3r/GUI/ImGuiDoubleSlider.cpp

@@ -316,6 +316,16 @@ bool ImGuiControl::IsLClickOnThumb()
     return false;
 }
 
+bool ImGuiControl::IsLClickOnHoveredPos()
+{
+    if (m_lclick_on_hovered_pos) {
+        // Discard left mouse click at hovered tick to avoud reuse it on next frame
+        m_lclick_on_hovered_pos = false;
+        return true;
+    }
+    return false;
+}
+
 void ImGuiControl::draw_scroll_line(const ImRect& scroll_line, const ImRect& slideable_region)
 {
     if (m_cb_draw_scroll_line)
@@ -542,8 +552,8 @@ bool ImGuiControl::draw_slider( int* higher_pos, int* lower_pos,
         ImGui::ItemHoverable(m_regions.lower_thumb, id) && context.IO.MouseClicked[0])
         m_selection = ssLower;
 
-    // detect left click on selected thumb
     {
+        // detect left click on selected thumb
         const ImRect& active_thumb = m_selection == ssHigher ? m_regions.higher_thumb : m_regions.lower_thumb;
         if (ImGui::ItemHoverable(active_thumb, id) && context.IO.MouseClicked[0]) {
             m_active_thumb = active_thumb;
@@ -561,6 +571,19 @@ bool ImGuiControl::draw_slider( int* higher_pos, int* lower_pos,
             // invalidate active thumb clicking
             m_active_thumb = ImRect(0.f, 0.f, 0.f, 0.f);
         }
+
+        // detect left click on hovered region
+        if (ImGui::ItemHoverable(m_hovered_region, id) && context.IO.MouseClicked[0]) {
+            // clear active ID to avoid a process of behavior()
+            if (context.ActiveId == id && context.ActiveIdSource == ImGuiInputSource_Mouse)
+                ImGui::ClearActiveID();
+        }
+        else if (ImGui::ItemHoverable(m_hovered_region, id) && context.IO.MouseReleased[0]) {
+            const ImRect& slideable_region = m_selection == ssHigher ? m_regions.higher_slideable_region : m_regions.lower_slideable_region;
+            if (lclicked_on_thumb(id, slideable_region, m_min_pos, m_max_pos, m_hovered_region, m_flags)) {
+                m_lclick_on_hovered_pos = true;
+            }
+        }
     }
 
     // update thumb position

src/slic3r/GUI/ImGuiDoubleSlider.hpp

@@ -90,6 +90,7 @@ public:
 
     bool    IsRClickOnThumb() const     { return m_rclick_on_selected_thumb; }
     bool    IsLClickOnThumb();
+    bool    IsLClickOnHoveredPos();
 
     bool    is_horizontal() const       { return !(m_flags & ImGuiSliderFlags_Vertical); }
     bool    render();
@@ -98,6 +99,9 @@ public:
     float   rounding() const            { return m_draw_opts.rounding(); }
     ImVec2  left_dummy_sz() const       { return m_draw_opts.text_dummy_sz() + m_draw_opts.text_padding(); }
 
+    void    SetHoveredRegion(ImRect region) { m_hovered_region = region; }
+    void    InvalidateHoveredRegion()       { m_hovered_region = ImRect(0.f, 0.f, 0.f, 0.f); }
+
     void    set_get_label_on_move_cb(std::function<std::string(int)> cb)                    { m_cb_get_label_on_move = cb; }
     void    set_get_label_cb(std::function<std::string(int)> cb)                            { m_cb_get_label = cb; }
     void    set_draw_scroll_line_cb(std::function<void(const ImRect&, const ImRect&)> cb)   { m_cb_draw_scroll_line = cb; }
@@ -148,8 +152,10 @@ private:
 
     bool            m_rclick_on_selected_thumb{ false };
     bool            m_lclick_on_selected_thumb{ false };
+    bool            m_lclick_on_hovered_pos   { false };
     bool            m_suppress_process_behavior{ false };
     ImRect          m_active_thumb;
+    ImRect          m_hovered_region;
 
     bool            m_draw_lower_thumb{ true };
     bool            m_combine_thumbs  { false };