ProgressBar: added indeterminate mode by passing an animated negative value. (#5316, #5370, #1901)

docs/CHANGELOG.txt

@@ -64,6 +64,8 @@ Other changes:
   duplicate with this fix. (#7399, #7404) [@GamingMinds-DanielC]
 - TreeNode: Added ImGuiTreeNodeFlags_SpanTextWidth to make hitbox and highlight only
   cover the label. (#6937) [@dimateos]
+- ProgressBar: Added support for indeterminate progress bar by passing an animated
+  negative fraction, e.g. ProgressBar(-1.0f * GetTime()). (#5316, #5370, #1901)[@gan74]
 - Text, DrawList: Improved handling of long single-line wrapped text. Faster and
   mitigitate issues with reading vertex indexing limits with 16-bit indices. (#7496, #5720)
 - Backends: OpenGL: Detect ES3 contexts on desktop based on version string,

imgui_demo.cpp

@@ -1909,6 +1909,11 @@ static void ShowDemoWindowWidgets()
         char buf[32];
         sprintf(buf, "%d/%d", (int)(progress_saturated * 1753), 1753);
         ImGui::ProgressBar(progress, ImVec2(0.f, 0.f), buf);
+
+        ImGui::ProgressBar(-1.0f * (float)ImGui::GetTime(), ImVec2(0.0f, 0.0f), "Searching..");
+        ImGui::SameLine(0.0f, ImGui::GetStyle().ItemInnerSpacing.x);
+        ImGui::Text("Indeterminate");
+
         ImGui::TreePop();
     }
 

imgui_widgets.cpp

@@ -1291,27 +1291,47 @@ void ImGui::ProgressBar(float fraction, const ImVec2& size_arg, const char* over
     if (!ItemAdd(bb, 0))
         return;
 
+    // Fraction < 0.0f will display an indeterminate progress bar animation
+    // The value must be animated along with time, so e.g. passing '-1.0f * ImGui::GetTime()' as fraction works.
+    const bool is_indeterminate = (fraction < 0.0f);
+    if (!is_indeterminate)
+        fraction = ImSaturate(fraction);
+
     // Out of courtesy we accept a NaN fraction without crashing
-    fraction = ImSaturate(fraction);
-    const float fraction_not_nan = (fraction == fraction) ? fraction : 0.0f;
+    float fill_n0 = 0.0f;
+    float fill_n1 = (fraction == fraction) ? fraction : 0.0f;
+
+    if (is_indeterminate)
+    {
+        const float fill_width_n = 0.2f;
+        fill_n0 = ImFmod(-fraction, 1.0f) * (1.0f + fill_width_n) - fill_width_n;
+        fill_n1 = ImSaturate(fill_n0 + fill_width_n);
+        fill_n0 = ImSaturate(fill_n0);
+    }
 
     // Render
     RenderFrame(bb.Min, bb.Max, GetColorU32(ImGuiCol_FrameBg), true, style.FrameRounding);
     bb.Expand(ImVec2(-style.FrameBorderSize, -style.FrameBorderSize));
-    const ImVec2 fill_br = ImVec2(ImLerp(bb.Min.x, bb.Max.x, fraction_not_nan), bb.Max.y);
-    RenderRectFilledRangeH(window->DrawList, bb, GetColorU32(ImGuiCol_PlotHistogram), 0.0f, fraction_not_nan, style.FrameRounding);
+    RenderRectFilledRangeH(window->DrawList, bb, GetColorU32(ImGuiCol_PlotHistogram), fill_n0, fill_n1, style.FrameRounding);
 
     // Default displaying the fraction as percentage string, but user can override it
-    char overlay_buf[32];
-    if (!overlay)
+    // Don't display text for indeterminate bars by default
+    if (!is_indeterminate || overlay != NULL)
     {
-        ImFormatString(overlay_buf, IM_ARRAYSIZE(overlay_buf), "%.0f%%", fraction * 100 + 0.01f);
-        overlay = overlay_buf;
-    }
+        char overlay_buf[32];
+        if (!overlay)
+        {
+            ImFormatString(overlay_buf, IM_ARRAYSIZE(overlay_buf), "%.0f%%", fraction * 100 + 0.01f);
+            overlay = overlay_buf;
+        }
 
-    ImVec2 overlay_size = CalcTextSize(overlay, NULL);
-    if (overlay_size.x > 0.0f)
-        RenderTextClipped(ImVec2(ImClamp(fill_br.x + style.ItemSpacing.x, bb.Min.x, bb.Max.x - overlay_size.x - style.ItemInnerSpacing.x), bb.Min.y), bb.Max, overlay, NULL, &overlay_size, ImVec2(0.0f, 0.5f), &bb);
+        ImVec2 overlay_size = CalcTextSize(overlay, NULL);
+        if (overlay_size.x > 0.0f)
+        {
+            float text_x = is_indeterminate ? (bb.Min.x + bb.Max.x - overlay_size.x) * 0.5f : ImLerp(bb.Min.x, bb.Max.x, fill_n1) + style.ItemSpacing.x;
+            RenderTextClipped(ImVec2(ImClamp(text_x, bb.Min.x, bb.Max.x - overlay_size.x - style.ItemInnerSpacing.x), bb.Min.y), bb.Max, overlay, NULL, &overlay_size, ImVec2(0.0f, 0.5f), &bb);
+        }
+    }
 }
 
 void ImGui::Bullet()