1 files changed, 116 insertions, 0 deletions
diff --git a/quantum/painter/qp_draw_ellipse.c b/quantum/painter/qp_draw_ellipse.c
new file mode 100644
index 0000000000..7f2f4abcfd
--- /dev/null
+++ b/quantum/painter/qp_draw_ellipse.c
@@ -0,0 +1,116 @@
+// Copyright 2021 Paul Cotter (@gr1mr3aver)
+// Copyright 2021 Nick Brassel (@tzarc)
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "qp_internal.h"
+#include "qp_comms.h"
+#include "qp_draw.h"
+
+// Utilize 4-way symmetry to draw an ellipse
+static bool qp_ellipse_helper_impl(painter_device_t device, uint16_t centerx, uint16_t centery, uint16_t offsetx, uint16_t offsety, bool filled) {
+    /*
+    Ellipses have the property of 4-way symmetry, so four pixels can be drawn
+    for each computed [offsetx,offsety] given the center coordinates
+    represented by [centerx,centery].
+
+    For filled ellipses, we can draw horizontal lines between each pair of
+    pixels with the same final value of y.
+
+    When offsetx == 0 only two pixels can be drawn for filled or unfilled ellipses
+    */
+
+    int16_t xpx = ((int16_t)centerx) + ((int16_t)offsetx);
+    int16_t xmx = ((int16_t)centerx) - ((int16_t)offsetx);
+    int16_t ypy = ((int16_t)centery) + ((int16_t)offsety);
+    int16_t ymy = ((int16_t)centery) - ((int16_t)offsety);
+
+    if (offsetx == 0) {
+        if (!qp_internal_setpixel_impl(device, xpx, ypy)) {
+            return false;
+        }
+        if (!qp_internal_setpixel_impl(device, xpx, ymy)) {
+            return false;
+        }
+    } else if (filled) {
+        if (!qp_internal_fillrect_helper_impl(device, xpx, ypy, xmx, ypy)) {
+            return false;
+        }
+        if (offsety > 0 && !qp_internal_fillrect_helper_impl(device, xpx, ymy, xmx, ymy)) {
+            return false;
+        }
+    } else {
+        if (!qp_internal_setpixel_impl(device, xpx, ypy)) {
+            return false;
+        }
+        if (!qp_internal_setpixel_impl(device, xpx, ymy)) {
+            return false;
+        }
+        if (!qp_internal_setpixel_impl(device, xmx, ypy)) {
+            return false;
+        }
+        if (!qp_internal_setpixel_impl(device, xmx, ymy)) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+// Quantum Painter External API: qp_ellipse
+
+bool qp_ellipse(painter_device_t device, uint16_t x, uint16_t y, uint16_t sizex, uint16_t sizey, uint8_t hue, uint8_t sat, uint8_t val, bool filled) {
+    qp_dprintf("qp_ellipse: entry\n");
+    struct painter_driver_t *driver = (struct painter_driver_t *)device;
+    if (!driver->validate_ok) {
+        qp_dprintf("qp_ellipse: fail (validation_ok == false)\n");
+        return false;
+    }
+
+    int16_t aa = ((int16_t)sizex) * ((int16_t)sizex);
+    int16_t bb = ((int16_t)sizey) * ((int16_t)sizey);
+    int16_t fa = 4 * ((int16_t)aa);
+    int16_t fb = 4 * ((int16_t)bb);
+
+    int16_t dx = 0;
+    int16_t dy = ((int16_t)sizey);
+
+    qp_internal_fill_pixdata(device, QP_MAX(sizex, sizey), hue, sat, val);
+
+    if (!qp_comms_start(device)) {
+        qp_dprintf("qp_ellipse: fail (could not start comms)\n");
+        return false;
+    }
+
+    bool ret = true;
+    for (int16_t delta = (2 * bb) + (aa * (1 - (2 * sizey))); bb * dx <= aa * dy; dx++) {
+        if (!qp_ellipse_helper_impl(device, x, y, dx, dy, filled)) {
+            ret = false;
+            break;
+        }
+        if (delta >= 0) {
+            delta += fa * (1 - dy);
+            dy--;
+        }
+        delta += bb * (4 * dx + 6);
+    }
+
+    dx = sizex;
+    dy = 0;
+
+    for (int16_t delta = (2 * aa) + (bb * (1 - (2 * sizex))); aa * dy <= bb * dx; dy++) {
+        if (!qp_ellipse_helper_impl(device, x, y, dx, dy, filled)) {
+            ret = false;
+            break;
+        }
+        if (delta >= 0) {
+            delta += fb * (1 - dx);
+            dx--;
+        }
+        delta += aa * (4 * dy + 6);
+    }
+
+    qp_dprintf("qp_ellipse: %s\n", ret ? "ok" : "fail");
+    qp_comms_stop(device);
+    return ret;
+}