RGB matrix effect - left-right gradient (#7742)

* Left-right gradient.

* Update the comment to match the new functionality.

* CPP does integer division so this round is not necessary.

* The x-range is actually 224, update comment and use bit-shifting again.

* Update docs with gradient left-right effect and associated "DISABLE" option.

1 files changed, 22 insertions, 0 deletions

diff --git a/quantum/rgb_matrix_animations/gradient_left_right_anim.h b/quantum/rgb_matrix_animations/gradient_left_right_anim.h
new file mode 100644
index 0000000000..2eab2eb759
--- /dev/null
+++ b/quantum/rgb_matrix_animations/gradient_left_right_anim.h
@@ -0,0 +1,22 @@
+#ifndef DISABLE_RGB_MATRIX_GRADIENT_LEFT_RIGHT
+RGB_MATRIX_EFFECT(GRADIENT_LEFT_RIGHT)
+#    ifdef RGB_MATRIX_CUSTOM_EFFECT_IMPLS
+
+bool GRADIENT_LEFT_RIGHT(effect_params_t* params) {
+    RGB_MATRIX_USE_LIMITS(led_min, led_max);
+
+    HSV     hsv   = rgb_matrix_config.hsv;
+    uint8_t scale = scale8(64, rgb_matrix_config.speed);
+    for (uint8_t i = led_min; i < led_max; i++) {
+        RGB_MATRIX_TEST_LED_FLAGS();
+        // The x range will be 0..224, map this to 0..7
+        // Relies on hue being 8-bit and wrapping
+        hsv.h   = rgb_matrix_config.hsv.h + (scale * g_led_config.point[i].x >> 5);
+        RGB rgb = hsv_to_rgb(hsv);
+        rgb_matrix_set_color(i, rgb.r, rgb.g, rgb.b);
+    }
+    return led_max < DRIVER_LED_TOTAL;
+}
+
+#    endif  // RGB_MATRIX_CUSTOM_EFFECT_IMPLS
+#endif      // DISABLE_RGB_MATRIX_GRADIENT_LEFT_RIGHT