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Feat: Add ImPlotPieChartFlags_NoSliceBorder and custom pie renderers #679

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Feat: Add ImPlotPieChartFlags_NoSliceBorder and custom pie renderers #679

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21aa68b
feat: add ImPlotPieChartFlags_NoSliceBorder and custom pie renderers
brenocq Feb 17, 2026
5287e43
docs: simplify NoSliceBorder flag docs
brenocq Feb 17, 2026
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9 changes: 5 additions & 4 deletions implot.h
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Original file line number Diff line number Diff line change
Expand Up @@ -316,10 +316,11 @@ enum ImPlotInfLinesFlags_ {

// Flags for PlotPieChart. Used by setting ImPlotSpec::Flags.
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_Exploding = 1 << 12 // Explode legend-hovered slice
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_Exploding = 1 << 12, // explode legend-hovered slice
ImPlotPieChartFlags_NoSliceBorder = 1 << 13 // do not draw slice borders
};

// Flags for PlotHeatmap. Used by setting ImPlotSpec::Flags.
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3 changes: 2 additions & 1 deletion implot_demo.cpp
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Expand Up @@ -651,11 +651,12 @@ void Demo_PieCharts() {
CHECKBOX_FLAG(flags, ImPlotPieChartFlags_Normalize);
CHECKBOX_FLAG(flags, ImPlotPieChartFlags_IgnoreHidden);
CHECKBOX_FLAG(flags, ImPlotPieChartFlags_Exploding);
CHECKBOX_FLAG(flags, ImPlotPieChartFlags_NoSliceBorder);

if (ImPlot::BeginPlot("##Pie1", ImVec2(ImGui::GetTextLineHeight()*16,ImGui::GetTextLineHeight()*16), ImPlotFlags_Equal | ImPlotFlags_NoMouseText)) {
ImPlot::SetupAxes(nullptr, nullptr, ImPlotAxisFlags_NoDecorations, ImPlotAxisFlags_NoDecorations);
ImPlot::SetupAxesLimits(0, 1, 0, 1);
ImPlot::PlotPieChart(labels1, data1, 4, 0.5, 0.5, 0.4, "%.2f", 90, {ImPlotProp_Flags, flags});
ImPlot::PlotPieChart(labels1, data1, 4, 0.5, 0.5, 0.4, "%.2f", 90, {ImPlotProp_FillAlpha, 0.5, ImPlotProp_Flags, flags});
ImPlot::EndPlot();
}

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106 changes: 100 additions & 6 deletions implot_items.cpp
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Expand Up @@ -2455,7 +2455,100 @@ 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, bool detached = false) {
IMPLOT_INLINE void PrimPieSliceFill(ImDrawList& draw_list, const ImVec2* points, int count, ImU32 col, const ImVec2& uv) {
// Write vertices
for (int i = 0; i < count; ++i) {
draw_list._VtxWritePtr[i].pos = points[i];
draw_list._VtxWritePtr[i].uv = uv;
draw_list._VtxWritePtr[i].col = col;
}
draw_list._VtxWritePtr += count;

// Write indices as a triangle fan (all triangles share first vertex - the center)
for (int i = 2; i < count; ++i) {
draw_list._IdxWritePtr[0] = (ImDrawIdx)(draw_list._VtxCurrentIdx);
draw_list._IdxWritePtr[1] = (ImDrawIdx)(draw_list._VtxCurrentIdx + i - 1);
draw_list._IdxWritePtr[2] = (ImDrawIdx)(draw_list._VtxCurrentIdx + i);
draw_list._IdxWritePtr += 3;
}
draw_list._VtxCurrentIdx += count;
}

IMPLOT_INLINE void PrimPieSliceLine(ImDrawList& draw_list, const ImVec2* points, int count, ImU32 col, float half_weight, const ImVec2& tex_uv0, const ImVec2& tex_uv1) {
// Create a thick polyline by drawing quads between each segment
const int segments = count - 1;

for (int i = 0; i < segments; ++i) {
const ImVec2& p1 = points[i];
const ImVec2& p2 = points[i + 1];

// Calculate perpendicular vector for line thickness (same as PrimLine)
float dx = p2.x - p1.x;
float dy = p2.y - p1.y;
IMPLOT_NORMALIZE2F_OVER_ZERO(dx, dy);
dx *= half_weight;
dy *= half_weight;

// Four vertices for the quad (same layout as PrimLine)
draw_list._VtxWritePtr[0].pos.x = p1.x + dy;
draw_list._VtxWritePtr[0].pos.y = p1.y - dx;
draw_list._VtxWritePtr[0].uv = tex_uv0;
draw_list._VtxWritePtr[0].col = col;

draw_list._VtxWritePtr[1].pos.x = p2.x + dy;
draw_list._VtxWritePtr[1].pos.y = p2.y - dx;
draw_list._VtxWritePtr[1].uv = tex_uv0;
draw_list._VtxWritePtr[1].col = col;

draw_list._VtxWritePtr[2].pos.x = p2.x - dy;
draw_list._VtxWritePtr[2].pos.y = p2.y + dx;
draw_list._VtxWritePtr[2].uv = tex_uv1;
draw_list._VtxWritePtr[2].col = col;

draw_list._VtxWritePtr[3].pos.x = p1.x - dy;
draw_list._VtxWritePtr[3].pos.y = p1.y + dx;
draw_list._VtxWritePtr[3].uv = tex_uv1;
draw_list._VtxWritePtr[3].col = col;

draw_list._VtxWritePtr += 4;

// Two triangles for the quad
const ImDrawIdx vtx_idx = (ImDrawIdx)(draw_list._VtxCurrentIdx);
draw_list._IdxWritePtr[0] = vtx_idx;
draw_list._IdxWritePtr[1] = vtx_idx + 1;
draw_list._IdxWritePtr[2] = vtx_idx + 2;
draw_list._IdxWritePtr[3] = vtx_idx;
draw_list._IdxWritePtr[4] = vtx_idx + 2;
draw_list._IdxWritePtr[5] = vtx_idx + 3;
draw_list._IdxWritePtr += 6;

draw_list._VtxCurrentIdx += 4;
}
}

IMPLOT_INLINE void RenderPieSliceFill(ImDrawList& draw_list, ImVec2* buffer, int count, ImU32 col) {
const ImVec2 uv = draw_list._Data->TexUvWhitePixel;
// Reserve space for vertices and indices
// Triangle fan: n-2 triangles for n vertices, so (n-2)*3 indices
const int idx_count = (count - 2) * 3;
draw_list.PrimReserve(idx_count, count);
PrimPieSliceFill(draw_list, buffer, count, col, uv);
}

IMPLOT_INLINE void RenderPieSliceLine(ImDrawList& draw_list, ImVec2* buffer, int count, ImU32 col) {
float half_weight = 1.0f; // Weight of 2.0f -> half_weight of 1.0f
ImVec2 tex_uv0, tex_uv1;
GetLineRenderProps(draw_list, half_weight, tex_uv0, tex_uv1);

// Polyline with n points has n-1 segments, each needs 4 vertices and 6 indices
const int segments = count - 1;
const int vtx_count = segments * 4;
const int idx_count = segments * 6;
draw_list.PrimReserve(idx_count, vtx_count);
PrimPieSliceLine(draw_list, buffer, count, col, half_weight, tex_uv0, tex_uv1);
}

IMPLOT_INLINE void RenderPieSlice(ImDrawList& draw_list, const ImPlotPoint& center, double radius, double a0, double a1, ImU32 col, ImPlotPieChartFlags flags, bool detached = false) {
const float resolution = 50 / (2 * IM_PI);
ImVec2 buffer[52];

Expand Down Expand Up @@ -2500,10 +2593,11 @@ IMPLOT_INLINE void RenderPieSlice(ImDrawList& draw_list, const ImPlotPoint& cent
buffer[i + 1] = buffer[0];

// fill
draw_list.AddConvexPolyFilled(buffer, n + 2, col);
RenderPieSliceFill(draw_list, buffer, n + 2, col);

// border (for AA)
draw_list.AddPolyline(buffer, n + 2, col, 0, 2.0f);
if (!ImHasFlag(flags, ImPlotPieChartFlags_NoSliceBorder))
RenderPieSliceLine(draw_list, buffer, n + 2, col);
}

template <typename T>
Expand Down Expand Up @@ -2556,11 +2650,11 @@ void PlotPieChartEx(const char* const label_ids[], IndexerIdx<T> indexer, ImPlot
if (sum > 0.0) {
ImU32 col = GetCurrentItem()->Color;
if (percent < 0.5) {
RenderPieSlice(draw_list, center, radius, a0, a1, col, hovered);
RenderPieSlice(draw_list, center, radius, a0, a1, col, spec.Flags, hovered);
}
else {
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);
RenderPieSlice(draw_list, center, radius, a0, a0 + (a1 - a0) * 0.5, col, spec.Flags, hovered);
RenderPieSlice(draw_list, center, radius, a0 + (a1 - a0) * 0.5, a1, col, spec.Flags, hovered);
}
}
EndItem();
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