feat: add ImPlotPieChartFlags_Exploding (#592)

epezent · Dec 24, 2024 · 35f7955 · 35f7955
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commit 35f7955
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Showing 4 changed files with 52 additions and 15 deletions.
diff --git a/TODO.md b/TODO.md
@@ -15,7 +15,6 @@ The list below represents a combination of high-priority work, nice-to-have feat
 
 - add `PlotBubbles` (see MATLAB bubble chart)
 - add non-zero references for `PlotBars` etc.
-- add exploding to `PlotPieChart` (on hover-highlight?)
 - fix appearance of `PlotBars` spacing
 
 ## Styling
@@ -80,6 +79,7 @@ Ideally every `PlotX` function should use our faster rendering pipeline when it
 |PlotDummy|-|-|-|-|
 
 ## Completed
+- add exploding to `PlotPieChart` (on legend hover)
 - make BeginPlot take fewer args:
 - make query a tool -> `DragRect`
 - rework DragLine/Point to use ButtonBehavior

diff --git a/implot.h b/implot.h
@@ -289,7 +289,8 @@ enum ImPlotInfLinesFlags_ {
 enum ImPlotPieChartFlags_ {
     ImPlotPieChartFlags_None         = 0,       // default
     ImPlotPieChartFlags_Normalize    = 1 << 10, // force normalization of pie chart values (i.e. always make a full circle if sum < 0)
-    ImPlotPieChartFlags_IgnoreHidden = 1 << 11  // ignore hidden slices when drawing the pie chart (as if they were not there)
+    ImPlotPieChartFlags_IgnoreHidden = 1 << 11, // ignore hidden slices when drawing the pie chart (as if they were not there)
+    ImPlotPieChartFlags_Exploding    = 1 << 12  // Explode legend-hovered slice
 };
 
 // Flags for PlotHeatmap

diff --git a/implot_demo.cpp b/implot_demo.cpp
@@ -615,6 +615,7 @@ void Demo_PieCharts() {
     ImGui::DragFloat4("Values", data1, 0.01f, 0, 1);
     CHECKBOX_FLAG(flags, ImPlotPieChartFlags_Normalize);
     CHECKBOX_FLAG(flags, ImPlotPieChartFlags_IgnoreHidden);
+    CHECKBOX_FLAG(flags, ImPlotPieChartFlags_Exploding);
 
     if (ImPlot::BeginPlot("##Pie1", ImVec2(250,250), ImPlotFlags_Equal | ImPlotFlags_NoMouseText)) {
         ImPlot::SetupAxes(nullptr, nullptr, ImPlotAxisFlags_NoDecorations, ImPlotAxisFlags_NoDecorations);

diff --git a/implot_items.cpp b/implot_items.cpp
@@ -2200,20 +2200,53 @@ CALL_INSTANTIATE_FOR_NUMERIC_TYPES()
 // [SECTION] PlotPieChart
 //-----------------------------------------------------------------------------
 
-IMPLOT_INLINE void RenderPieSlice(ImDrawList& draw_list, const ImPlotPoint& center, double radius, double a0, double a1, ImU32 col) {
+IMPLOT_INLINE void RenderPieSlice(ImDrawList& draw_list, const ImPlotPoint& center, double radius, double a0, double a1, ImU32 col, bool detached = false) {
     const float resolution = 50 / (2 * IM_PI);
     ImVec2 buffer[52];
-    buffer[0] = PlotToPixels(center,IMPLOT_AUTO,IMPLOT_AUTO);
+
     int n = ImMax(3, (int)((a1 - a0) * resolution));
     double da = (a1 - a0) / (n - 1);
     int i = 0;
-    for (; i < n; ++i) {
-        double a = a0 + i * da;
-        buffer[i + 1] = PlotToPixels(center.x + radius * cos(a), center.y + radius * sin(a),IMPLOT_AUTO,IMPLOT_AUTO);
-    }
-    buffer[i+1] = buffer[0];
+
+    if (detached) {
+        const double offset = 0.08; // Offset of the detached slice
+        const double width_scale = 0.95; // Scale factor for the width of the detached slice
+
+        double a_mid = (a0 + a1) / 2;
+        double new_a0 = a_mid - (a1 - a0) * width_scale / 2;
+        double new_a1 = a_mid + (a1 - a0) * width_scale / 2;
+        double new_da = (new_a1 - new_a0) / (n - 1);
+
+        ImPlotPoint offsetCenter(center.x + offset * cos(a_mid), center.y + offset * sin(a_mid));
+
+        // Start point (center of the offset)
+        buffer[0] = PlotToPixels(offsetCenter, IMPLOT_AUTO, IMPLOT_AUTO);
+
+        for (; i < n; ++i) {
+            double a = new_a0 + i * new_da;
+            buffer[i + 1] = PlotToPixels(
+                offsetCenter.x + (radius + offset/2) * cos(a),
+                offsetCenter.y + (radius + offset/2) * sin(a),
+                IMPLOT_AUTO, IMPLOT_AUTO
+            );
+        }
+
+    } else {
+        buffer[0] = PlotToPixels(center, IMPLOT_AUTO, IMPLOT_AUTO);
+        for (; i < n; ++i) {
+            double a = a0 + i * da;
+            buffer[i + 1] = PlotToPixels(
+                center.x + radius * cos(a), 
+                center.y + radius * sin(a), 
+                IMPLOT_AUTO, IMPLOT_AUTO);
+        }
+    }
+    // Close the shape
+    buffer[i + 1] = buffer[0];
+
     // fill
-    draw_list.AddConvexPolyFilled(buffer, n + 1, col);
+    draw_list.AddConvexPolyFilled(buffer, n + 2, col);
+
     // border (for AA)
     draw_list.AddPolyline(buffer, n + 2, col, 0, 2.0f);
 }
@@ -2257,21 +2290,21 @@ void PlotPieChartEx(const char* const label_ids[], const T* values, int count, I
     ImPlotPoint Pmax = ImPlotPoint(center.x + radius, center.y + radius);
     for (int i = 0; i < count; ++i) {
         ImPlotItem* item = GetItem(label_ids[i]);
-
         const double percent = normalize ? (double)values[i] / sum : (double)values[i];
         const bool skip      = sum <= 0.0 || (ignore_hidden && item != nullptr && !item->Show);
         if (!skip)
             a1 = a0 + 2 * IM_PI * percent;
 
         if (BeginItemEx(label_ids[i], FitterRect(Pmin, Pmax))) {
+            const bool hovered = ImPlot::IsLegendEntryHovered(label_ids[i]) && ImHasFlag(flags, ImPlotPieChartFlags_Exploding);
             if (sum > 0.0) {
                 ImU32 col = GetCurrentItem()->Color;
                 if (percent < 0.5) {
-                    RenderPieSlice(draw_list, center, radius, a0, a1, col);
+                    RenderPieSlice(draw_list, center, radius, a0, a1, col, hovered);
                 }
                 else {
-                    RenderPieSlice(draw_list, center, radius, a0, a0 + (a1 - a0) * 0.5, col);
-                    RenderPieSlice(draw_list, center, radius, a0 + (a1 - a0) * 0.5, a1, col);
+                    RenderPieSlice(draw_list, center, radius, a0, a0 + (a1 - a0) * 0.5, col, hovered);
+                    RenderPieSlice(draw_list, center, radius, a0 + (a1 - a0) * 0.5, a1, col, hovered);
                 }
             }
             EndItem();
@@ -2323,7 +2356,9 @@ void PlotPieChart(const char* const label_ids[], const T* values, int count, dou
                     fmt((double)values[i], buffer, 32, fmt_data);
                     ImVec2 size = ImGui::CalcTextSize(buffer);
                     double angle = a0 + (a1 - a0) * 0.5;
-                    ImVec2 pos = PlotToPixels(center.x + 0.5 * radius * cos(angle), center.y + 0.5 * radius * sin(angle), IMPLOT_AUTO, IMPLOT_AUTO);
+                    const bool hovered = ImPlot::IsLegendEntryHovered(label_ids[i]) && ImHasFlag(flags, ImPlotPieChartFlags_Exploding);
+                    const double offset = (hovered ? 0.6 : 0.5) * radius; 
+                    ImVec2 pos = PlotToPixels(center.x + offset * cos(angle), center.y + offset * sin(angle), IMPLOT_AUTO, IMPLOT_AUTO);
                     ImU32 col = CalcTextColor(ImGui::ColorConvertU32ToFloat4(item->Color));
                     draw_list.AddText(pos - size * 0.5f, col, buffer);
                 }