[examples] Added shapes_pie_chart (#5227)

* Added shapes_pie_chart example

* Made the example colorful

* Added some interactivity to the example

* Revert top comment to the standard

* Remove unused MAX_SLICES constant

---------

Co-authored-by: Gideon Serfontein <gse@newspacesystems.com>
Co-authored-by: Ray <raysan5@gmail.com>

examples/shapes/shapes_pie_chart.c

@@ -0,0 +1,224 @@
+/*******************************************************************************************
+*
+*   raylib [shapes] example - pie chart
+*
+*   Example complexity rating: [★★☆☆] 2/4
+*
+*   Example originally created with raylib 5.6-dev, last time updated with raylib 5.6-dev
+*
+*   Example contributed by Gideon Serfontein (@GideonSerf) and reviewed by Ramon Santamaria (@raysan5)
+*
+*   Example licensed under an unmodified zlib/libpng license, which is an OSI-certified,
+*   BSD-like license that allows static linking with closed source software
+*
+*   Copyright (c) 2025 Gideon Serfontein (@GideonSerf)
+*
+********************************************************************************************/
+
+#include "raylib.h"
+#include <math.h>
+#include <stdio.h>
+
+#define RAYGUI_IMPLEMENTATION
+#include "raygui.h"
+
+//------------------------------------------------------------------------------------
+// Program main entry point
+//------------------------------------------------------------------------------------
+int main(void)
+{
+    // Initialization
+    //--------------------------------------------------------------------------------------
+    const int screenWidth = 800;
+    const int screenHeight = 450;
+
+    InitWindow(screenWidth, screenHeight, "raylib [shapes] example - interactive pie chart");
+
+    #define MAX_SLICES 10
+    int sliceCount = 7;
+    float values[MAX_SLICES] = {300.0f, 100.0f, 450.0f, 350.0f, 600.0f, 380.0f, 750.0f}; //initial slice values
+    char labels[MAX_SLICES][32];
+    bool editingLabel[MAX_SLICES] = {false};
+
+    for (int i = 0; i < MAX_SLICES; i++)
+        snprintf(labels[i], 32, "Slice %i", i + 1);
+
+    bool showValues = true;
+    bool showPercentages = false;
+    int hoveredSlice = -1;
+    Rectangle scrollPanelBounds = {0};
+    Vector2 scrollContentOffset = {0};
+    Rectangle view = {0};
+
+    SetTargetFPS(60);
+    //--------------------------------------------------------------------------------------
+
+    // Main game loop
+    while (!WindowShouldClose())
+    {
+        // Update
+        //----------------------------------------------------------------------------------
+        //UI layout parameters
+        const int panelWidth = 270;
+        const int panelMargin = 5;
+
+        // UI Panel top-left anchor
+        const Vector2 panelPos = {
+            (float)screenWidth  - panelMargin - panelWidth,
+            (float)panelMargin
+        };
+
+        // UI Panel rectangle
+        const Rectangle panelRect = {
+            panelPos.x, panelPos.y,
+            (float)panelWidth,
+            (float)screenHeight - 2.0f*panelMargin
+        };
+
+        // Pie chart geometry
+        const Rectangle canvas = { 0, 0, panelPos.x, (float)screenHeight };
+        const Vector2 center = {canvas.width / 2.0f, canvas.height / 2.0f};
+        const float radius = 205.0f;
+
+        // Calculate total value for percentage calculations
+        float totalValue = 0.0f;
+        for (int i = 0; i < sliceCount; i++)
+            totalValue += values[i];
+
+        // Check for mouse hover over slices
+        hoveredSlice = -1; // Reset hovered slice
+        Vector2 mousePos = GetMousePosition();
+        if (CheckCollisionPointRec(mousePos, canvas)) // Only check if mouse is inside the canvas
+        {
+            float dx = mousePos.x - center.x;
+            float dy = mousePos.y - center.y;
+            float distance = sqrtf(dx * dx + dy * dy);
+
+            if (distance <= radius) // Inside the pie radius
+            {
+                float angle = atan2f(dy, dx) * RAD2DEG;
+                if (angle < 0)
+                    angle += 360;
+
+                float currentAngle = 0.0f;
+                for (int i = 0; i < sliceCount; i++)
+                {
+                    float sweep = (totalValue > 0) ? (values[i] / totalValue) * 360.0f : 0.0f;
+                    if (angle >= currentAngle && angle < (currentAngle + sweep))
+                    {
+                        hoveredSlice = i;
+                        break;
+                    }
+                    currentAngle += sweep;
+                }
+            }
+        }
+        //----------------------------------------------------------------------------------
+
+        // Draw
+        //----------------------------------------------------------------------------------
+        BeginDrawing();
+        ClearBackground(RAYWHITE);
+
+        // Draw the pie chart on the canvas
+        //------------------------------------------------------------------------------
+        float startAngle = 0.0f;
+        for (int i = 0; i < sliceCount; i++)
+        {
+            float sweepAngle = (totalValue > 0) ? (values[i] / totalValue) * 360.0f : 0.0f;
+            float midAngle = startAngle + sweepAngle / 2.0f; // Middle angle for label positioning
+
+            Color color = ColorFromHSV((float)i / sliceCount * 360.0f, 0.75f, 0.9f);
+            float currentRadius = radius;
+
+            // Make the hovered slice pop out by adding 5 pixels to its radius
+            if (i == hoveredSlice)
+                currentRadius += 5.0f;
+
+            // Draw the pie slice using raylib's DrawCircleSector function
+            DrawCircleSector(center, currentRadius, startAngle, startAngle + sweepAngle, 120, color);
+
+            // Draw the label for the current slice
+            if (values[i] > 0)
+            {
+                char labelText[64];
+                if (showValues && showPercentages)
+                    snprintf(labelText, 64, "%.1f (%.0f%%)", values[i], (values[i] / totalValue) * 100.0f);
+                else if (showValues)
+                    snprintf(labelText, 64, "%.1f", values[i]);
+                else if (showPercentages)
+                    snprintf(labelText, 64, "%.0f%%", (values[i] / totalValue) * 100.0f);
+                else
+                    labelText[0] = '\0';
+
+                Vector2 textSize = MeasureTextEx(GetFontDefault(), labelText, 18, 1);
+                float labelRadius = radius * 0.7f;
+                Vector2 labelPos = {
+                    center.x + cosf(midAngle * DEG2RAD) * labelRadius - textSize.x / 2,
+                    center.y + sinf(midAngle * DEG2RAD) * labelRadius - textSize.y / 2};
+                DrawText(labelText, (int)labelPos.x, (int)labelPos.y, 18, WHITE);
+            }
+
+            startAngle += sweepAngle;
+        }
+        //------------------------------------------------------------------------------
+
+        // UI control panel
+        //------------------------------------------------------------------------------
+        DrawRectangleRec(panelRect, Fade(LIGHTGRAY, 0.5f));
+        DrawRectangleLinesEx(panelRect, 1.0f, GRAY);
+
+        int currentY = (int)panelPos.y + 12; // Start a bit lower for margin
+
+        GuiSpinner((Rectangle){ panelPos.x + 95, (float)currentY, 125, 25 }, "Slices ", &sliceCount, 1, MAX_SLICES, false);
+        currentY += 40;
+
+        GuiCheckBox((Rectangle){ panelPos.x + 20, (float)currentY, 20, 20 }, "Show Values", &showValues);
+        currentY += 30;
+
+        GuiCheckBox((Rectangle){ panelPos.x + 20, (float)currentY, 20, 20 }, "Show Percentages", &showPercentages);
+        currentY += 40;
+
+        GuiLine((Rectangle){ panelPos.x + 10, (float)currentY, panelRect.width - 20, 1 }, NULL);
+        currentY += 20;
+
+        // Scrollable area for slice editors
+        scrollPanelBounds = (Rectangle){ panelPos.x+panelMargin, (float)currentY, panelRect.width-panelMargin*2, panelRect.y + panelRect.height - currentY - panelMargin };
+        int contentHeight = sliceCount * 35;
+
+        GuiScrollPanel(scrollPanelBounds, NULL,
+                       (Rectangle){ 0, 0, panelRect.width - 20, (float)contentHeight },
+                       &scrollContentOffset, &view);
+
+        const float contentX = view.x + scrollContentOffset.x; // left of content
+        const float contentY = view.y + scrollContentOffset.y; // top of content
+
+        BeginScissorMode((int)view.x, (int)view.y, (int)view.width, (int)view.height);
+        for (int i = 0; i < sliceCount; i++)
+        {
+            const int rowY = (int)(contentY + 5 + i * 35);
+
+            // Color indicator
+            Color color = ColorFromHSV((float)i / sliceCount * 360.0f, 0.75f, 0.9f);
+            DrawRectangle((int)(contentX + 15), rowY + 5, 20, 20, color);
+
+            // Label textbox
+            if (GuiTextBox((Rectangle){contentX + 45, (float)rowY, 75, 30}, labels[i], 32, editingLabel[i]))
+                editingLabel[i] = !editingLabel[i];
+
+            GuiSliderBar((Rectangle){contentX + 130, (float)rowY, 110, 30},
+                         NULL, NULL, &values[i], 0.0f, 1000.0f);
+        }
+        EndScissorMode();
+
+        EndDrawing();
+        //----------------------------------------------------------------------------------
+    }
+
+    // De-Initialization
+    //--------------------------------------------------------------------------------------
+    CloseWindow(); // Close window and OpenGL context
+    //--------------------------------------------------------------------------------------
+
+    return 0;
+}