led-multicolor: Scale to RGB colors to LEDs max brightness

Otherwise we might exceed max brightness and get -EINVAL.

Tested-by: Chris Vogel <chris@ween.de>
Reported-by: Chris Vogel <chris@ween.de>
Closes: https://gitlab.freedesktop.org/agx/feedbackd/-/issues/95
Signed-off-by: Guido Günther <agx@sigxcpu.org>

src/fbd-dev-led-multicolor.c

@@ -15,6 +15,8 @@
 
 #include <gio/gio.h>
 
+#include <math.h>
+
 #define LED_MULTI_INDEX_ATTR     "multi_index"
 #define LED_MULTI_INDEX_RED      "red"
 #define LED_MULTI_INDEX_GREEN    "green"
@@ -132,11 +134,14 @@ fbd_dev_led_multicolor_set_color (FbdDevLed           *led,
     colors[priv->green_index] = 0;
     colors[priv->blue_index] = max_brightness;
     break;
-  case FBD_FEEDBACK_LED_COLOR_RGB:
+  case FBD_FEEDBACK_LED_COLOR_RGB: {
-    colors[priv->red_index] = rgb->r;
+    float scale = max_brightness / 255.0;
-    colors[priv->green_index] = rgb->g;
+    /* RGB colors are 0..255 so we need to scale to 0..max_brightness */
-    colors[priv->blue_index] = rgb->b;
+    colors[priv->red_index] = MIN (max_brightness, roundf (rgb->r * scale));
+    colors[priv->green_index] = MIN (max_brightness, roundf (rgb->g * scale));
+    colors[priv->blue_index] = MIN (max_brightness, roundf (rgb->b * scale));
     break;
+  }
   default:
     g_warning("Unhandled color: %d\n", color);
     return FALSE;

src/meson.build

@@ -38,7 +38,17 @@ if get_option('daemon')
     'fbd-udev.c',
   ]
 
-  fbd_deps = [gio, gio_unix, glib, gmobile, gobject, gsound, gudev, json_glib]
+  fbd_deps = [
+    gio,
+    gio_unix,
+    glib,
+    gmobile,
+    gobject,
+    gsound,
+    gudev,
+    json_glib,
+    cc.find_library('m', required: false),
+  ]
 
   fbd_inc = [include_directories('.'), libfeedback_inc, dbus_inc]