Added GetScrollX(), GetScrollX(), GetScrollMaxX() apis + demo (#246)

imgui.cpp

@@ -1475,8 +1475,8 @@ ImGuiWindow::ImGuiWindow(const char* name)
     SizeContents = SizeContentsExplicit = ImVec2(0.0f, 0.0f);
     WindowPadding = ImVec2(0.0f, 0.0f);
     Scroll = ImVec2(0.0f, 0.0f);
-    ScrollTargetRelY = FLT_MAX;
-    ScrollTargetCenterRatioY = 0.5f;
+    ScrollTarget = ImVec2(FLT_MAX, FLT_MAX);
+    ScrollTargetCenterRatio = ImVec2(0.5f, 0.5f);
     ScrollbarX = ScrollbarY = false;
     ScrollbarSizes = ImVec2(0.0f, 0.0f);
     Active = WasActive = false;
@@ -3730,11 +3730,16 @@ bool ImGui::Begin(const char* name, bool* p_opened, const ImVec2& size_on_first_
         window->FocusIdxAllRequestNext = window->FocusIdxTabRequestNext = IM_INT_MAX;
 
         // Apply scrolling
-        if (window->ScrollTargetRelY < FLT_MAX)
+        if (window->ScrollTarget.x < FLT_MAX)
         {
-            float center_ratio_y = window->ScrollTargetCenterRatioY;
-            window->Scroll.y = window->ScrollTargetRelY - ((1.0f - center_ratio_y) * window->TitleBarHeight()) - (center_ratio_y * window->SizeFull.y);
-            window->ScrollTargetRelY = FLT_MAX;
+            window->Scroll.x = window->ScrollTarget.x;
+            window->ScrollTarget.x = FLT_MAX;
+        }
+        if (window->ScrollTarget.y < FLT_MAX)
+        {
+            float center_ratio = window->ScrollTargetCenterRatio.y;
+            window->Scroll.y = window->ScrollTarget.y - ((1.0f - center_ratio) * window->TitleBarHeight()) - (center_ratio * window->SizeFull.y);
+            window->ScrollTarget.y = FLT_MAX;
         }
         window->Scroll = ImMax(window->Scroll, ImVec2(0.0f, 0.0f));
         if (!window->Collapsed && !window->SkipItems)
@@ -4738,23 +4743,40 @@ void ImGui::SetCursorScreenPos(const ImVec2& screen_pos)
     window->DC.CursorPos = screen_pos;
 }
 
+float ImGui::GetScrollX()
+{
+    return GImGui->CurrentWindow->Scroll.x;
+}
+
 float ImGui::GetScrollY()
+{
+    return GImGui->CurrentWindow->Scroll.y;
+}
+
+float ImGui::GetScrollMaxX()
 {
     ImGuiWindow* window = GetCurrentWindowRead();
-    return window->Scroll.y;
+    return window->SizeContents.x - window->SizeFull.x - window->ScrollbarSizes.x;
 }
 
 float ImGui::GetScrollMaxY()
 {
     ImGuiWindow* window = GetCurrentWindowRead();
-    return window->SizeContents.y - window->SizeFull.y;
+    return window->SizeContents.y - window->SizeFull.y - window->ScrollbarSizes.y;
+}
+
+void ImGui::SetScrollX(float scroll_x)
+{
+    ImGuiWindow* window = GetCurrentWindow();
+    window->ScrollTarget.x = scroll_x;
+    window->ScrollTargetCenterRatio.x = 0.0f;
 }
 
 void ImGui::SetScrollY(float scroll_y)
 {
     ImGuiWindow* window = GetCurrentWindow();
-    window->ScrollTargetRelY = scroll_y + window->TitleBarHeight(); // title bar height cancelled out when using ScrollTargetRelY
-    window->ScrollTargetCenterRatioY = 0.0f;
+    window->ScrollTarget.y = scroll_y + window->TitleBarHeight(); // title bar height canceled out when using ScrollTargetRelY
+    window->ScrollTargetCenterRatio.y = 0.0f;
 }
 
 void ImGui::SetScrollFromPosY(float pos_y, float center_y_ratio)
@@ -4762,10 +4784,10 @@ void ImGui::SetScrollFromPosY(float pos_y, float center_y_ratio)
     // We store a target position so centering can occur on the next frame when we are guaranteed to have a known window size
     ImGuiWindow* window = GetCurrentWindow();
     IM_ASSERT(center_y_ratio >= 0.0f && center_y_ratio <= 1.0f);
-    window->ScrollTargetRelY = (float)(int)(pos_y + window->Scroll.y);
-    if (center_y_ratio <= 0.0f && window->ScrollTargetRelY <= window->WindowPadding.y)    // Minor hack to make "scroll to top" take account of WindowPadding, else it would scroll to (WindowPadding.y - ItemSpacing.y)
-        window->ScrollTargetRelY = 0.0f;
-    window->ScrollTargetCenterRatioY = center_y_ratio;
+    window->ScrollTarget.y = (float)(int)(pos_y + window->Scroll.y);
+    if (center_y_ratio <= 0.0f && window->ScrollTarget.y <= window->WindowPadding.y)    // Minor hack to make "scroll to top" take account of WindowPadding, else it would scroll to (WindowPadding.y - ItemSpacing.y)
+        window->ScrollTarget.y = 0.0f;
+    window->ScrollTargetCenterRatio.y = center_y_ratio;
 }
 
 // center_y_ratio: 0.0f top of last item, 0.5f vertical center of last item, 1.0f bottom of last item.

imgui.h

@@ -152,8 +152,11 @@ namespace ImGui
     IMGUI_API void          SetWindowCollapsed(const char* name, bool collapsed, ImGuiSetCond cond = 0);   // set named window collapsed state
     IMGUI_API void          SetWindowFocus(const char* name);                                              // set named window to be focused / front-most. use NULL to remove focus.
 
+    IMGUI_API float         GetScrollX();                                                       // get scrolling amount [0..GetScrollMaxX()]
     IMGUI_API float         GetScrollY();                                                       // get scrolling amount [0..GetScrollMaxY()]
-    IMGUI_API float         GetScrollMaxY();                                                    // get maximum scrolling amount == ContentSize.Y - WindowSize.Y
+    IMGUI_API float         GetScrollMaxX();                                                    // get maximum scrolling amount ~~ ContentSize.X - WindowSize.X
+    IMGUI_API float         GetScrollMaxY();                                                    // get maximum scrolling amount ~~ ContentSize.Y - WindowSize.Y
+    IMGUI_API void          SetScrollX(float scroll_x);                                         // set scrolling amount [0..GetScrollMaxX()]
     IMGUI_API void          SetScrollY(float scroll_y);                                         // set scrolling amount [0..GetScrollMaxY()]
     IMGUI_API void          SetScrollHere(float center_y_ratio = 0.5f);                         // adjust scrolling amount to make current cursor position visible. center_y_ratio=0.0: top, 0.5: center, 1.0: bottom.
     IMGUI_API void          SetScrollFromPosY(float pos_y, float center_y_ratio = 0.5f);        // adjust scrolling amount to make given position valid. use GetCursorPos() or GetCursorStartPos()+offset to get valid positions.

imgui_demo.cpp

@@ -912,7 +912,7 @@ void ImGui::ShowTestWindow(bool* opened)
             static bool track = true;
             static int track_line = 50, scroll_to_px = 200;
             ImGui::Checkbox("Track", &track);
-            ImGui::SameLine(130); track |= ImGui::DragInt("##line", &track_line, 0.25f, 0, 9999, "Line %.0f");
+            ImGui::SameLine(130); track |= ImGui::DragInt("##line", &track_line, 0.25f, 0, 99, "Line %.0f");
             bool scroll_to = ImGui::Button("Scroll To");
             ImGui::SameLine(130); scroll_to |= ImGui::DragInt("##pos_y", &scroll_to_px, 1.00f, 0, 9999, "y = %.0f px");
             if (scroll_to) track = false;
@@ -968,6 +968,16 @@ void ImGui::ShowTestWindow(bool* opened)
                 }
             }
             ImGui::EndChild();
+            float scroll_x_delta = 0.0f;
+            ImGui::SmallButton("<<"); if (ImGui::IsItemActive()) scroll_x_delta = -ImGui::GetIO().DeltaTime * 1000.0f;
+            ImGui::SameLine(); ImGui::Text("Scroll from code"); ImGui::SameLine(); 
+            ImGui::SmallButton(">>"); if (ImGui::IsItemActive()) scroll_x_delta = +ImGui::GetIO().DeltaTime * 1000.0f;
+            if (scroll_x_delta != 0.0f)
+            {
+                ImGui::BeginChild("scrolling"); // Demonstrate a trick: you can use Begin to set yourself in the context of another window (here we are already out of your child window)
+                ImGui::SetScrollX(ImGui::GetScrollX() + scroll_x_delta);
+                ImGui::End();
+            }
             ImGui::TreePop();
         }
 

imgui_internal.h

@@ -565,8 +565,8 @@ struct ImGuiWindow
     ImVec2                  WindowPadding;                      // Window padding at the time of begin. We need to lock it, in particular manipulation of the ShowBorder would have an effect
     ImGuiID                 MoveID;                             // == window->GetID("#MOVE")
     ImVec2                  Scroll;
-    float                   ScrollTargetRelY;                   // target scroll position. stored as cursor position with scrolling canceled out, so the highest point is always 0.0f. (FLT_MAX for no change)
-    float                   ScrollTargetCenterRatioY;           // 0.0f = scroll so that target position is at top, 0.5f = scroll so that target position is centered
+    ImVec2                  ScrollTarget;                       // target scroll position. stored as cursor position with scrolling canceled out, so the highest point is always 0.0f. (FLT_MAX for no change)
+    ImVec2                  ScrollTargetCenterRatio;            // 0.0f = scroll so that target position is at top, 0.5f = scroll so that target position is centered
     bool                    ScrollbarX, ScrollbarY;
     ImVec2                  ScrollbarSizes;                     // 
     bool                    Active;                             // Set to true on Begin()