Revert "Death to C++"

This reverts commit 066ac22605.

src/ui/ui_piano.cpp

@@ -0,0 +1,136 @@
+#include "ui/ui_piano.h"
+
+#define PIANO_BLACK_W     11.0f
+#define PIANO_BLACK_H_PCT 0.6f
+
+B32 piano_is_black_key(S32 note) {
+    S32 n = note % 12;
+    return n == 1 || n == 3 || n == 6 || n == 8 || n == 10;
+}
+
+// Velocity-based color: blue (vel 0) → green (mid) → red (vel 127)
+Clay_Color piano_velocity_color(S32 velocity) {
+    F32 t = (F32)velocity / 127.0f;
+    F32 r, g, b;
+    if (t < 0.5f) {
+        F32 s = t * 2.0f;
+        r = 40.0f  + s * (76.0f  - 40.0f);
+        g = 120.0f + s * (175.0f - 120.0f);
+        b = 220.0f + s * (80.0f  - 220.0f);
+    } else {
+        F32 s = (t - 0.5f) * 2.0f;
+        r = 76.0f  + s * (220.0f - 76.0f);
+        g = 175.0f + s * (50.0f  - 175.0f);
+        b = 80.0f  + s * (40.0f  - 80.0f);
+    }
+    return Clay_Color{r, g, b, 255};
+}
+
+void ui_piano(UI_PianoState *state, MidiEngine *midi, F32 avail_w, F32 avail_h) {
+    Clay_ElementId piano_id = CLAY_ID("PianoContainer");
+    CLAY(piano_id,
+        .layout = {
+            .sizing = { .width = CLAY_SIZING_GROW(), .height = CLAY_SIZING_GROW() },
+            .layoutDirection = CLAY_LEFT_TO_RIGHT,
+        }
+    ) {
+        // Compute black key size proportional to white keys
+        F32 black_key_h = avail_h * PIANO_BLACK_H_PCT;
+        if (black_key_h < uis(20)) black_key_h = uis(20);
+
+        F32 white_key_w = avail_w / 52.0f;
+        F32 black_key_w = white_key_w * 0.6f;
+        if (black_key_w < uis(8)) black_key_w = uis(8);
+
+        // White keys (grow to fill width and height)
+        for (S32 note = PIANO_FIRST_NOTE; note <= PIANO_LAST_NOTE; note++) {
+            if (piano_is_black_key(note)) continue;
+
+            B32 midi_held = midi_is_note_held(midi, note);
+            B32 mouse_held = state->mouse_note == note;
+            Clay_Color bg;
+            if (midi_held) {
+                bg = piano_velocity_color(midi_get_note_velocity(midi, note));
+            } else if (mouse_held) {
+                bg = g_theme.accent;
+            } else {
+                bg = Clay_Color{240, 240, 240, 255};
+            }
+
+            CLAY(CLAY_IDI("PKey", note),
+                .layout = {
+                    .sizing = { .width = CLAY_SIZING_GROW(), .height = CLAY_SIZING_GROW() },
+                },
+                .backgroundColor = bg,
+                .border = { .color = {190, 190, 190, 255}, .width = { .right = 1 } },
+            ) {}
+        }
+
+        // Black keys (floating, attached to left white key)
+        for (S32 note = PIANO_FIRST_NOTE; note <= PIANO_LAST_NOTE; note++) {
+            if (!piano_is_black_key(note)) continue;
+
+            Clay_ElementId parent_wkey = CLAY_IDI("PKey", note - 1);
+            B32 midi_held = midi_is_note_held(midi, note);
+            B32 mouse_held = state->mouse_note == note;
+            Clay_Color bg;
+            if (midi_held) {
+                bg = piano_velocity_color(midi_get_note_velocity(midi, note));
+            } else if (mouse_held) {
+                bg = g_theme.accent;
+            } else {
+                bg = Clay_Color{25, 25, 30, 255};
+            }
+
+            CLAY(CLAY_IDI("PKey", note),
+                .layout = {
+                    .sizing = {
+                        .width = CLAY_SIZING_FIXED(black_key_w),
+                        .height = CLAY_SIZING_FIXED(black_key_h),
+                    },
+                },
+                .backgroundColor = bg,
+                .cornerRadius = { .topLeft = 0, .topRight = 0, .bottomLeft = uis(2), .bottomRight = uis(2) },
+                .floating = {
+                    .parentId = parent_wkey.id,
+                    .zIndex = 100,
+                    .attachPoints = {
+                        .element = CLAY_ATTACH_POINT_CENTER_TOP,
+                        .parent = CLAY_ATTACH_POINT_RIGHT_TOP,
+                    },
+                    .attachTo = CLAY_ATTACH_TO_ELEMENT_WITH_ID,
+                },
+            ) {}
+        }
+    }
+}
+
+void ui_piano_update_input(UI_PianoState *state) {
+    PlatformInput input = g_wstate.input;
+
+    if (!input.mouse_down) {
+        state->mouse_note = -1;
+        return;
+    }
+
+    // Find hovered piano key — check black keys first (they're on top)
+    S32 hovered_note = -1;
+    for (S32 note = PIANO_FIRST_NOTE; note <= PIANO_LAST_NOTE; note++) {
+        if (piano_is_black_key(note) && Clay_PointerOver(CLAY_IDI("PKey", note))) {
+            hovered_note = note;
+            break;
+        }
+    }
+    if (hovered_note == -1) {
+        for (S32 note = PIANO_FIRST_NOTE; note <= PIANO_LAST_NOTE; note++) {
+            if (!piano_is_black_key(note) && Clay_PointerOver(CLAY_IDI("PKey", note))) {
+                hovered_note = note;
+                break;
+            }
+        }
+    }
+
+    if (hovered_note != -1) {
+        state->mouse_note = hovered_note;
+    }
+}