Added SetScrollY(), SetScrollFromPosY(). Renamed SetScrollPosHere() to SetScrollFromCursorPos(). (#150)

imgui.cpp

@@ -136,7 +136,8 @@
  Occasionally introducing changes that are breaking the API. The breakage are generally minor and easy to fix.
  Here is a change-log of API breaking changes, if you are using one of the functions listed, expect to have to fix some code.
  
- - 2015/07/01 (1.42) - renamed GetScrollPosY() to GetScrollY(). Necessary to reduce confusion along with other scrolling functions, because positions (e.g. cursor position) are not equivalent to scrolling amount.
+ - 2015/07/02 (1.42) - renamed SetScrollPosHere() to SetScrollFromCursorPos(). Kept inline redirection function (will obsolete).
+ - 2015/07/02 (1.42) - renamed GetScrollPosY() to GetScrollY(). Necessary to reduce confusion along with other scrolling functions, because positions (e.g. cursor position) are not equivalent to scrolling amount.
  - 2015/06/14 (1.41) - changed ImageButton() default bg_col parameter from (0,0,0,1) (black) to (0,0,0,0) (transparent) - makes a difference when texture have transparence
  - 2015/06/14 (1.41) - changed Selectable() API from (label, selected, size) to (label, selected, flags, size). Size override should have been rarely be used. Sorry!
  - 2015/05/31 (1.40) - renamed GetWindowCollapsed() to IsWindowCollapsed() for consistency. Kept inline redirection function (will obsolete).
@@ -339,7 +340,6 @@
  - window: resizing from any sides? + mouse cursor directives for app.
  - window: get size/pos helpers given names (see discussion in #249)
  - scrolling: add horizontal scroll
-!- scrolling: set scrolling given a position.
 !- scrolling: allow immediately effective change of scroll if we haven't appended items yet
  - widgets: display mode: widget-label, label-widget (aligned on column or using fixed size), label-newline-tab-widget etc.
  - widgets: clean up widgets internal toward exposing everything.
@@ -1419,7 +1419,7 @@ 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")
     float                   ScrollY;
-    float                   ScrollTargetRelY;                   // target scroll position. stored as cursor position with scrolling canceled out, so the highest point is always 0.0f. (-1.0f for no change)
+    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
     bool                    ScrollbarY;
     bool                    Active;                             // Set to true on Begin()
@@ -1786,7 +1786,7 @@ ImGuiWindow::ImGuiWindow(const char* name)
     SizeContents = ImVec2(0.0f, 0.0f);
     WindowPadding = ImVec2(0.0f, 0.0f);
     ScrollY = 0.0f;
-    ScrollTargetRelY = -1.0f;
+    ScrollTargetRelY = FLT_MAX;
     ScrollTargetCenterRatioY = 0.5f;
     ScrollbarY = false;
     Active = WasActive = false;
@@ -3858,11 +3858,11 @@ 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 >= 0.0f)
+        if (window->ScrollTargetRelY < FLT_MAX)
         {
             float center_ratio_y = window->ScrollTargetCenterRatioY;
             window->ScrollY = window->ScrollTargetRelY - ((1.0f - center_ratio_y) * window->TitleBarHeight()) - (center_ratio_y * window->SizeFull.y);
-            window->ScrollTargetRelY = -1.0f;
+            window->ScrollTargetRelY = FLT_MAX;
         }
         window->ScrollY = ImMax(window->ScrollY, 0.0f);
         if (!window->Collapsed && !window->SkipItems)
@@ -4505,8 +4505,7 @@ bool ImGui::IsRootWindowOrAnyChildFocused()
 
 float ImGui::GetWindowWidth()
 {
-    ImGuiState& g = *GImGui;
+    ImGuiWindow* window = GImGui->CurrentWindow;
-    ImGuiWindow* window = g.CurrentWindow;
     return window->Size.x;
 }
 
@@ -4828,19 +4827,31 @@ float ImGui::GetScrollMaxY()
     return window->SizeContents.y - window->SizeFull.y;
 }
 
-void ImGui::SetScrollPosHere(float center_y_ratio)
+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;
+}
+
+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
-    ImGuiState& g = *GImGui;
-    IM_ASSERT(center_y_ratio >= 0.0f && center_y_ratio <= 1.0f);
     ImGuiWindow* window = GetCurrentWindow();
-    window->ScrollTargetRelY = (float)(int)(window->ScrollY + window->DC.CursorPosPrevLine.y - window->Pos.y + (window->DC.PrevLineHeight) * center_y_ratio);
+    IM_ASSERT(center_y_ratio >= 0.0f && center_y_ratio <= 1.0f);
-    window->ScrollTargetRelY += g.Style.ItemSpacing.y * (center_y_ratio - 0.5f) * 2.0f;
+    window->ScrollTargetRelY = (float)(int)(pos_y + window->ScrollY);
     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;
 }
 
+void ImGui::SetScrollFromCursorPos(float center_y_ratio)
+{
+    ImGuiWindow* window = GetCurrentWindow();
+    float target_y = window->DC.CursorPosPrevLine.y + (window->DC.PrevLineHeight * center_y_ratio) + (GImGui->Style.ItemSpacing.y * (center_y_ratio - 0.5f) * 2.0f); // Precisely aim above, in the middle or below the last line.
+    ImGui::SetScrollFromPosY(target_y - window->Pos.y, center_y_ratio);
+}
+
 void ImGui::SetKeyboardFocusHere(int offset)
 {
     ImGuiWindow* window = GetCurrentWindow();
@@ -7751,7 +7762,7 @@ bool ImGui::Combo(const char* label, int* current_item, bool (*items_getter)(voi
                     *current_item = i;
                 }
                 if (item_selected && menu_toggled)
-                    ImGui::SetScrollPosHere();
+                    ImGui::SetScrollFromCursorPos();
                 ImGui::PopID();
             }
             ImGui::EndPopup();
@@ -11300,10 +11311,10 @@ void ImGui::ShowTestWindow(bool* opened)
             {
                 ImGui::Text("%04d: scrollable region", i);
                 if (goto_line && line == i)
-                    ImGui::SetScrollPosHere();
+                    ImGui::SetScrollFromCursorPos();
             }
             if (goto_line && line >= 100)
-                ImGui::SetScrollPosHere();
+                ImGui::SetScrollFromCursorPos();
             ImGui::EndChild();
 
             ImGui::SameLine();
@@ -11497,11 +11508,14 @@ void ImGui::ShowTestWindow(bool* opened)
 
         if (ImGui::TreeNode("Scrolling"))
         {
-            ImGui::TextWrapped("Use SetScrollPosHere() to scroll to a given position.");
+            ImGui::TextWrapped("Use SetScrollFromPos() or SetScrollFromCursorPos() to scroll to a given position.");
             static bool track = true;
-            static int track_line = 50;
+            static int track_line = 50, scroll_to_px = 200;
             ImGui::Checkbox("Track", &track);
-            ImGui::SameLine(); ImGui::SliderInt("##line", &track_line, 0, 99, "Line %.0f");
+            ImGui::SameLine(130); track |= ImGui::DragInt("##line", &track_line, 0.25f, 0, 9999, "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;
 
             for (int i = 0; i < 3; i++)
             {
@@ -11509,11 +11523,13 @@ void ImGui::ShowTestWindow(bool* opened)
                 ImGui::BeginGroup();
                 ImGui::Text(i == 0 ? "Top" : i == 1 ? "Center" : "Bottom");
                 ImGui::BeginChild(ImGui::GetID((void *)i), ImVec2(ImGui::GetWindowWidth() * 0.25f, 200.0f), true);
+                if (scroll_to)
+                    ImGui::SetScrollFromPosY(ImGui::GetCursorStartPos().y + scroll_to_px, i * 0.50f);
                 for (int line = 0; line < 100; line++)
                 {
                     ImGui::Text("Line %d", line);
                     if (track && line == track_line)
-                        ImGui::SetScrollPosHere(i * 0.50f); // 0.0f,0.5f,1.0f
+                        ImGui::SetScrollFromCursorPos(i * 0.50f); // 0.0f:top, 0.5f:center, 1.0f:bottom
                 }
                 ImGui::EndChild();
                 ImGui::EndGroup();
@@ -12272,7 +12288,7 @@ struct ExampleAppConsole
             ImGui::PopStyleColor();
         }
         if (ScrollToBottom)
-            ImGui::SetScrollPosHere();
+            ImGui::SetScrollFromCursorPos();
         ScrollToBottom = false;
         ImGui::PopStyleVar();
         ImGui::EndChild();

imgui.h

@@ -135,9 +135,11 @@ 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         GetScrollY();                                                       // get scrolling position [0..GetScrollMaxY()]
+    IMGUI_API float         GetScrollY();                                                       // get scrolling amount [0..GetScrollMaxY()]
-    IMGUI_API float         GetScrollMaxY();                                                    // get maximum scrolling position == ContentSize.Y - WindowSize.Y
+    IMGUI_API float         GetScrollMaxY();                                                    // get maximum scrolling amount == ContentSize.Y - WindowSize.Y
-    IMGUI_API void          SetScrollPosHere(float center_y_ratio = 0.5f);                      // adjust scrolling position to make the current cursor position visible. center_y_ratio=0.0: top, =0.5: center, =1.0: bottom.
+    IMGUI_API void          SetScrollY(float scroll_y);                                         // set scrolling amount [0..GetScrollMaxY()]
+    IMGUI_API void          SetScrollFromCursorPos(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_API void          SetKeyboardFocusHere(int offset = 0);                               // focus keyboard on the next widget. Use positive 'offset' to access sub components of a multiple component widget
     IMGUI_API void          SetStateStorage(ImGuiStorage* tree);                                // replace tree state storage with our own (if you want to manipulate it yourself, typically clear subsection of it)
     IMGUI_API ImGuiStorage* GetStateStorage();
@@ -409,6 +411,7 @@ namespace ImGui
     static inline bool      IsClipped(const ImVec2& size) { return !IsRectVisible(size); }     // OBSOLETE 1.38+
     static inline bool      IsRectClipped(const ImVec2& size) { return !IsRectVisible(size); } // OBSOLETE 1.39+
     static inline bool      IsMouseHoveringBox(const ImVec2& rect_min, const ImVec2& rect_max) { return IsMouseHoveringRect(rect_min, rect_max); }  // OBSOLETE 1.36+
+    static inline void      SetScrollPosHere() { SetScrollFromCursorPos(); }                   // OBSOLETE 1.42+
 #endif
 
 } // namespace ImGui