Scrolling: Made it possible for mouse wheel and navigation-triggered scrolling to override a call to SetScrollX()/SetScrollY(), making it possible to use a simpler stateless pattern for auto-scrolling.

Demo: Log, Console: Using a simpler stateless pattern for auto-scrolling.

docs/CHANGELOG.txt

@@ -67,6 +67,11 @@ Other Changes:
 - InputTextMultiline: Fixed vertical scrolling tracking glitch.
 - Word-wrapping: Fixed overzealous word-wrapping when glyph edge lands exactly on the limit. Because
   of this, auto-fitting exactly unwrapped text would make it wrap. (fixes initial 1.15 commit, 78645a7d).
+- Scrolling: Made it possible for mouse wheel and navigation-triggered scrolling to override a call to
+  SetScrollX()/SetScrollY(), making it possible to use a simpler stateless pattern for auto-scrolling:
+     // (Submit items..)
+     if (ImGui::GetScrollY() >= ImGui::GetScrollMaxY())   // Keep scrolling at the bottom if already
+         ImGui::SetScrollHereY(1.0f);
 - Scrolling: Added SetScrollHereX(), SetScrollFromPosX() for completeness. (#1580) [@kevreco]
 - Style: Attenuated default opacity of ImGuiCol_Separator in Classic and Light styles.
 - Style: Added style.ColorButtonPosition (left/right, defaults to ImGuiDir_Right) to move the color button
@@ -86,6 +91,7 @@ Other Changes:
 - ImDrawListSplitter: Fixed memory leak when using low-level split api (was not affecting ImDrawList api,
   also this type was added in 1.71 and not advertised as a public-facing feature).
 - Fonts: binary_to_compressed_c.cpp: Display an error message if failing to open/read the input font file.
+- Demo: Log, Console: Using a simpler stateless pattern for auto-scrolling.
 - Backends: DX10/DX11: Backup, clear and restore Geometry Shader is any is bound when calling renderer.
 - Backends: DX11: Clear Hull Shader, Domain Shader, Compute Shader before rendering. Not backing/restoring them.
 - Backends: OSX: Disabled default native Mac clipboard copy/paste implementation in core library (added in 1.71),

imgui.cpp

@@ -3506,7 +3506,7 @@ void ImGui::UpdateMouseWheel()
         {
             float max_step = window->InnerRect.GetHeight() * 0.67f;
             float scroll_step = ImFloor(ImMin(5 * window->CalcFontSize(), max_step));
-            SetWindowScrollY(window, window->Scroll.y - wheel_y * scroll_step);
+            SetScrollY(window, window->Scroll.y - wheel_y * scroll_step);
         }
     }
 
@@ -3521,7 +3521,7 @@ void ImGui::UpdateMouseWheel()
         {
             float max_step = window->InnerRect.GetWidth() * 0.67f;
             float scroll_step = ImFloor(ImMin(2 * window->CalcFontSize(), max_step));
-            SetWindowScrollX(window, window->Scroll.x - wheel_x * scroll_step);
+            SetScrollX(window, window->Scroll.x - wheel_x * scroll_step);
         }
     }
 }
@@ -6524,16 +6524,6 @@ ImVec2 ImGui::GetWindowPos()
     return window->Pos;
 }
 
-void ImGui::SetWindowScrollX(ImGuiWindow* window, float new_scroll_x)
-{
-    window->Scroll.x = new_scroll_x;
-}
-
-void ImGui::SetWindowScrollY(ImGuiWindow* window, float new_scroll_y)
-{
-    window->Scroll.y = new_scroll_y;
-}
-
 void ImGui::SetWindowPos(ImGuiWindow* window, const ImVec2& pos, ImGuiCond cond)
 {
     // Test condition (NB: bit 0 is always true) and clear flags for next time
@@ -6921,6 +6911,18 @@ void ImGui::SetScrollY(float scroll_y)
     window->ScrollTargetCenterRatio.y = 0.0f;
 }
 
+void ImGui::SetScrollX(ImGuiWindow* window, float new_scroll_x)
+{
+    window->ScrollTarget.x = new_scroll_x;
+    window->ScrollTargetCenterRatio.x = 0.0f;
+}
+
+void ImGui::SetScrollY(ImGuiWindow* window, float new_scroll_y)
+{
+    window->ScrollTarget.y = new_scroll_y;
+    window->ScrollTargetCenterRatio.y = 0.0f;
+}
+
 void ImGui::SetScrollFromPosX(float local_x, float center_x_ratio)
 {
     // We store a target position so centering can occur on the next frame when we are guaranteed to have a known window size
@@ -8333,9 +8335,9 @@ static void ImGui::NavUpdate()
         if (window->DC.NavLayerActiveMask == 0x00 && window->DC.NavHasScroll && g.NavMoveRequest)
         {
             if (g.NavMoveDir == ImGuiDir_Left || g.NavMoveDir == ImGuiDir_Right)
-                SetWindowScrollX(window, ImFloor(window->Scroll.x + ((g.NavMoveDir == ImGuiDir_Left) ? -1.0f : +1.0f) * scroll_speed));
+                SetScrollX(window, ImFloor(window->Scroll.x + ((g.NavMoveDir == ImGuiDir_Left) ? -1.0f : +1.0f) * scroll_speed));
             if (g.NavMoveDir == ImGuiDir_Up || g.NavMoveDir == ImGuiDir_Down)
-                SetWindowScrollY(window, ImFloor(window->Scroll.y + ((g.NavMoveDir == ImGuiDir_Up) ? -1.0f : +1.0f) * scroll_speed));
+                SetScrollY(window, ImFloor(window->Scroll.y + ((g.NavMoveDir == ImGuiDir_Up) ? -1.0f : +1.0f) * scroll_speed));
         }
 
         // *Normal* Manual scroll with NavScrollXXX keys
@@ -8343,12 +8345,12 @@ static void ImGui::NavUpdate()
         ImVec2 scroll_dir = GetNavInputAmount2d(ImGuiNavDirSourceFlags_PadLStick, ImGuiInputReadMode_Down, 1.0f/10.0f, 10.0f);
         if (scroll_dir.x != 0.0f && window->ScrollbarX)
         {
-            SetWindowScrollX(window, ImFloor(window->Scroll.x + scroll_dir.x * scroll_speed));
+            SetScrollX(window, ImFloor(window->Scroll.x + scroll_dir.x * scroll_speed));
             g.NavMoveFromClampedRefRect = true;
         }
         if (scroll_dir.y != 0.0f)
         {
-            SetWindowScrollY(window, ImFloor(window->Scroll.y + scroll_dir.y * scroll_speed));
+            SetScrollY(window, ImFloor(window->Scroll.y + scroll_dir.y * scroll_speed));
             g.NavMoveFromClampedRefRect = true;
         }
     }
@@ -8466,9 +8468,9 @@ static float ImGui::NavUpdatePageUpPageDown(int allowed_dir_flags)
         {
             // Fallback manual-scroll when window has no navigable item
             if (IsKeyPressed(g.IO.KeyMap[ImGuiKey_PageUp], true))
-                SetWindowScrollY(window, window->Scroll.y - window->InnerRect.GetHeight());
+                SetScrollY(window, window->Scroll.y - window->InnerRect.GetHeight());
             else if (IsKeyPressed(g.IO.KeyMap[ImGuiKey_PageDown], true))
-                SetWindowScrollY(window, window->Scroll.y + window->InnerRect.GetHeight());
+                SetScrollY(window, window->Scroll.y + window->InnerRect.GetHeight());
         }
         else
         {

imgui_demo.cpp

@@ -3449,7 +3449,7 @@ struct ExampleAppConsole
         Commands.push_back("CLEAR");
         Commands.push_back("CLASSIFY");  // "classify" is only here to provide an example of "C"+[tab] completing to "CL" and displaying matches.
         AutoScroll = true;
-        ScrollToBottom = true;
+        ScrollToBottom = false;
         AddLog("Welcome to Dear ImGui!");
     }
     ~ExampleAppConsole()
@@ -3470,7 +3470,6 @@ struct ExampleAppConsole
         for (int i = 0; i < Items.Size; i++)
             free(Items[i]);
         Items.clear();
-        ScrollToBottom = true;
     }
 
     void    AddLog(const char* fmt, ...) IM_FMTARGS(2)
@@ -3483,8 +3482,6 @@ struct ExampleAppConsole
         buf[IM_ARRAYSIZE(buf)-1] = 0;
         va_end(args);
         Items.push_back(Strdup(buf));
-        if (AutoScroll)
-            ScrollToBottom = true;
     }
 
     void    Draw(const char* title, bool* p_open)
@@ -3513,8 +3510,7 @@ struct ExampleAppConsole
         if (ImGui::SmallButton("Add Dummy Text"))  { AddLog("%d some text", Items.Size); AddLog("some more text"); AddLog("display very important message here!"); } ImGui::SameLine();
         if (ImGui::SmallButton("Add Dummy Error")) { AddLog("[error] something went wrong"); } ImGui::SameLine();
         if (ImGui::SmallButton("Clear")) { ClearLog(); } ImGui::SameLine();
-        bool copy_to_clipboard = ImGui::SmallButton("Copy"); ImGui::SameLine();
+        bool copy_to_clipboard = ImGui::SmallButton("Copy");
-        if (ImGui::SmallButton("Scroll to bottom")) ScrollToBottom = true;
         //static float t = 0.0f; if (ImGui::GetTime() - t > 0.02f) { t = ImGui::GetTime(); AddLog("Spam %f", t); }
 
         ImGui::Separator();
@@ -3522,9 +3518,7 @@ struct ExampleAppConsole
         // Options menu
         if (ImGui::BeginPopup("Options"))
         {
-            if (ImGui::Checkbox("Auto-scroll", &AutoScroll))
+            ImGui::Checkbox("Auto-scroll", &AutoScroll);
-                if (AutoScroll)
-                    ScrollToBottom = true;
             ImGui::EndPopup();
         }
 
@@ -3573,9 +3567,11 @@ struct ExampleAppConsole
         }
         if (copy_to_clipboard)
             ImGui::LogFinish();
-        if (ScrollToBottom)
+
+        if (ScrollToBottom || (AutoScroll && ImGui::GetScrollY() >= ImGui::GetScrollMaxY()))
             ImGui::SetScrollHereY(1.0f);
         ScrollToBottom = false;
+
         ImGui::PopStyleVar();
         ImGui::EndChild();
         ImGui::Separator();
@@ -3767,13 +3763,11 @@ struct ExampleAppLog
     ImGuiTextBuffer     Buf;
     ImGuiTextFilter     Filter;
     ImVector<int>       LineOffsets;        // Index to lines offset. We maintain this with AddLog() calls, allowing us to have a random access on lines
-    bool                AutoScroll;
+    bool                AutoScroll;     // Keep scrolling if already at the bottom
-    bool                ScrollToBottom;
 
     ExampleAppLog()
     {
         AutoScroll = true;
-        ScrollToBottom = false;
         Clear();
     }
 
@@ -3794,8 +3788,6 @@ struct ExampleAppLog
         for (int new_size = Buf.size(); old_size < new_size; old_size++)
             if (Buf[old_size] == '\n')
                 LineOffsets.push_back(old_size + 1);
-        if (AutoScroll)
-            ScrollToBottom = true;
     }
 
     void    Draw(const char* title, bool* p_open = NULL)
@@ -3809,9 +3801,7 @@ struct ExampleAppLog
         // Options menu
         if (ImGui::BeginPopup("Options"))
         {
-            if (ImGui::Checkbox("Auto-scroll", &AutoScroll))
+            ImGui::Checkbox("Auto-scroll", &AutoScroll);
-                if (AutoScroll)
-                    ScrollToBottom = true;
             ImGui::EndPopup();
         }
 
@@ -3876,9 +3866,9 @@ struct ExampleAppLog
         }
         ImGui::PopStyleVar();
 
-        if (ScrollToBottom)
+        if (AutoScroll && ImGui::GetScrollY() >= ImGui::GetScrollMaxY())
             ImGui::SetScrollHereY(1.0f);
-        ScrollToBottom = false;
+
         ImGui::EndChild();
         ImGui::End();
     }

imgui_internal.h

@@ -1460,8 +1460,8 @@ namespace ImGui
     IMGUI_API ImVec2        CalcWindowExpectedSize(ImGuiWindow* window);
     IMGUI_API bool          IsWindowChildOf(ImGuiWindow* window, ImGuiWindow* potential_parent);
     IMGUI_API bool          IsWindowNavFocusable(ImGuiWindow* window);
-    IMGUI_API void          SetWindowScrollX(ImGuiWindow* window, float new_scroll_x);
+    IMGUI_API void          SetScrollX(ImGuiWindow* window, float new_scroll_x);
-    IMGUI_API void          SetWindowScrollY(ImGuiWindow* window, float new_scroll_y);
+    IMGUI_API void          SetScrollY(ImGuiWindow* window, float new_scroll_y);
     IMGUI_API ImRect        GetWindowAllowedExtentRect(ImGuiWindow* window);
     IMGUI_API void          SetWindowPos(ImGuiWindow* window, const ImVec2& pos, ImGuiCond cond = 0);
     IMGUI_API void          SetWindowSize(ImGuiWindow* window, const ImVec2& size, ImGuiCond cond = 0);

imgui_widgets.cpp

@@ -3637,8 +3637,8 @@ bool ImGui::InputTextEx(const char* label, const char* hint, char* buf, int buf_
 
         if (IsKeyPressedMap(ImGuiKey_LeftArrow))                        { state->OnKeyPressed((is_startend_key_down ? STB_TEXTEDIT_K_LINESTART : is_wordmove_key_down ? STB_TEXTEDIT_K_WORDLEFT : STB_TEXTEDIT_K_LEFT) | k_mask); }
         else if (IsKeyPressedMap(ImGuiKey_RightArrow))                  { state->OnKeyPressed((is_startend_key_down ? STB_TEXTEDIT_K_LINEEND : is_wordmove_key_down ? STB_TEXTEDIT_K_WORDRIGHT : STB_TEXTEDIT_K_RIGHT) | k_mask); }
-        else if (IsKeyPressedMap(ImGuiKey_UpArrow) && is_multiline)     { if (io.KeyCtrl) SetWindowScrollY(draw_window, ImMax(draw_window->Scroll.y - g.FontSize, 0.0f)); else state->OnKeyPressed((is_startend_key_down ? STB_TEXTEDIT_K_TEXTSTART : STB_TEXTEDIT_K_UP) | k_mask); }
+        else if (IsKeyPressedMap(ImGuiKey_UpArrow) && is_multiline)     { if (io.KeyCtrl) SetScrollY(draw_window, ImMax(draw_window->Scroll.y - g.FontSize, 0.0f)); else state->OnKeyPressed((is_startend_key_down ? STB_TEXTEDIT_K_TEXTSTART : STB_TEXTEDIT_K_UP) | k_mask); }
-        else if (IsKeyPressedMap(ImGuiKey_DownArrow) && is_multiline)   { if (io.KeyCtrl) SetWindowScrollY(draw_window, ImMin(draw_window->Scroll.y + g.FontSize, GetScrollMaxY())); else state->OnKeyPressed((is_startend_key_down ? STB_TEXTEDIT_K_TEXTEND : STB_TEXTEDIT_K_DOWN) | k_mask); }
+        else if (IsKeyPressedMap(ImGuiKey_DownArrow) && is_multiline)   { if (io.KeyCtrl) SetScrollY(draw_window, ImMin(draw_window->Scroll.y + g.FontSize, GetScrollMaxY())); else state->OnKeyPressed((is_startend_key_down ? STB_TEXTEDIT_K_TEXTEND : STB_TEXTEDIT_K_DOWN) | k_mask); }
         else if (IsKeyPressedMap(ImGuiKey_Home))                        { state->OnKeyPressed(io.KeyCtrl ? STB_TEXTEDIT_K_TEXTSTART | k_mask : STB_TEXTEDIT_K_LINESTART | k_mask); }
         else if (IsKeyPressedMap(ImGuiKey_End))                         { state->OnKeyPressed(io.KeyCtrl ? STB_TEXTEDIT_K_TEXTEND | k_mask : STB_TEXTEDIT_K_LINEEND | k_mask); }
         else if (IsKeyPressedMap(ImGuiKey_Delete) && !is_readonly)      { state->OnKeyPressed(STB_TEXTEDIT_K_DELETE | k_mask); }