[lvgl] Add utility gradient function (#16048)

esphome/components/lvgl/gradient.py

@@ -1,3 +1,5 @@
+from operator import itemgetter
+
 from esphome import config_validation as cv
 import esphome.codegen as cg
 from esphome.const import (
@@ -11,6 +13,7 @@ from esphome.core import ID
 from esphome.cpp_generator import MockObj
 
 from .defines import CONF_GRADIENTS, CONF_OPA, LV_DITHER, add_define, add_warning
+from .helpers import add_lv_use
 from .lv_validation import lv_color, lv_percentage, opacity
 from .lvcode import lv
 from .types import lv_color_t, lv_gradient_t, lv_opa_t
@@ -50,6 +53,7 @@ GRADIENT_SCHEMA = cv.ensure_list(
 
 
 async def gradients_to_code(config):
+    add_lv_use("gradient")
     max_stops = 2
     if any(CONF_DITHER in x for x in config.get(CONF_GRADIENTS, ())):
         add_warning(
@@ -58,7 +62,7 @@ async def gradients_to_code(config):
     for gradient in config.get(CONF_GRADIENTS, ()):
         var = MockObj(cg.new_Pvariable(gradient[CONF_ID]), "->")
         idbase = gradient[CONF_ID].id
-        stops = gradient[CONF_STOPS]
+        stops = sorted(gradient[CONF_STOPS], key=itemgetter(CONF_POSITION))
         max_stops = max(max_stops, len(stops))
         if gradient[CONF_DIRECTION].startswith("VER"):
             lv.grad_vertical_init(var)

esphome/components/lvgl/lvgl_esphome.cpp

@@ -864,6 +864,32 @@ void lv_scale_draw_event_cb(lv_event_t *e, int16_t range_start, int16_t range_en
 }
 #endif  // USE_LVGL_SCALE
 
+#ifdef USE_LVGL_GRADIENT
+/**
+ *
+ * @param dsc The gradient descriptor containing the color stops
+ * @param pos The current position to calculate the color for
+ * @return The color for the given position
+ */
+
+lv_color_t lv_grad_calculate_color(const lv_grad_dsc_t *dsc, int32_t pos) {
+  if (dsc->stops_count == 0)
+    return lv_color_black();
+  if (dsc->stops_count == 1 || pos <= dsc->stops[0].frac)
+    return dsc->stops[0].color;
+  if (pos >= dsc->stops[dsc->stops_count - 1].frac)
+    return dsc->stops[dsc->stops_count - 1].color;
+  int i = 1;
+  while (i < dsc->stops_count && dsc->stops[i].frac < pos)
+    i++;
+  auto *stop1 = &dsc->stops[i - 1];
+  auto *stop2 = &dsc->stops[i];
+  int32_t range = stop2->frac - stop1->frac;
+  int32_t offset = pos - stop1->frac;
+  return lv_color_mix(stop2->color, stop1->color, range == 0 ? 0 : (offset * 255) / range);
+}
+#endif
+
 static void lv_container_constructor(const lv_obj_class_t *class_p, lv_obj_t *obj) {
   LV_TRACE_OBJ_CREATE("begin");
   LV_UNUSED(class_p);

esphome/components/lvgl/lvgl_esphome.h

@@ -115,6 +115,16 @@ inline void lv_animimg_set_src(lv_obj_t *img, std::vector<image::Image *> images
 int16_t lv_get_needle_angle_for_value(lv_obj_t *obj, int value);
 #endif
 
+#ifdef USE_LVGL_GRADIENT
+/**
+ *
+ * @param dsc The gradient descriptor containing the color stops
+ * @param pos The current position to calculate the color for
+ * @return The color for the given position
+ */
+
+lv_color_t lv_grad_calculate_color(const lv_grad_dsc_t *dsc, int32_t pos);
+#endif
 // Parent class for things that wrap an LVGL object
 class LvCompound {
  public:

esphome/core/defines.h

@@ -96,6 +96,7 @@
 #define USE_LVGL_CHECKBOX
 #define USE_LVGL_DROPDOWN
 #define USE_LVGL_FONT
+#define USE_LVGL_GRADIENT
 #define USE_LVGL_IMAGE
 #define USE_LVGL_IMAGEBUTTON
 #define USE_LVGL_KEY_LISTENER