NX: Don't change the background if the color has not really changed

graphics/Kconfig

@@ -25,9 +25,19 @@ config NX_NPLANES
 	int "Number of Color Planes"
 	default 1
 	---help---
-		Some YUV color formats requires support for multiple planes, one for each
-		color component.  Unless you have such special hardware, this value should be
-		undefined or set to 1.
+		Some YUV color formats requires support for multiple planes, one for
+		each color component.  Unless you have such special hardware (and
+		are willing to debug a lot of untested logic), this value should be
+		set to 1.
+
+config NX_BGCOLOR
+	hex "Initial background color"
+	default 0x0
+	---help---
+		NX will clear the background plane initially.  This is the default
+		color that will be used when the background is cleared.  Note: This
+		logic would have to be extended if you want to support multiple
+		color planes.
 
 config NX_WRITEONLY
 	bool "Write-only Graphics Device"

graphics/nxbe/nxbe_configure.c

@@ -49,6 +49,10 @@
  * Pre-Processor Definitions
  ****************************************************************************/
 
+#ifndef CONFIG_NX_BGCOLOR
+#  define CONFIG_NX_BGCOLOR 0
+#endif
+
 /****************************************************************************
  * Private Types
  ****************************************************************************/
@@ -57,6 +61,15 @@
  * Private Data
  ****************************************************************************/
 
+static const nxgl_mxpixel_t g_bgcolor[CONFIG_NX_NPLANES] =
+{
+  CONFIG_NX_BGCOLOR
+
+#if CONFIG_NX_NPLANES > 1
+#  warning Missing logic for multiple color planes
+#endif
+};
+
 /****************************************************************************
  * Public Data
  ****************************************************************************/
@@ -92,6 +105,10 @@ int nxbe_configure(FAR NX_DRIVERTYPE *dev, FAR struct nxbe_state_s *be)
       return ret;
     }
 
+  /* Set the initial background color */
+
+  nxgl_colorcopy(be->bgcolor, g_bgcolor);
+
   /* Check the number of color planes */
 
 #ifdef CONFIG_DEBUG

graphics/nxmu/nxmu_server.c

@@ -486,9 +486,18 @@ int nx_runinstance(FAR const char *mqname, FAR NX_DRIVERTYPE *dev)
 
          case NX_SVRMSG_SETBGCOLOR: /* Set the color of the background */
            {
-             FAR struct nxsvrmsg_setbgcolor_s *bgcolormsg = (FAR struct nxsvrmsg_setbgcolor_s *)buffer;
-             nxgl_colorcopy(fe.be.bgcolor, bgcolormsg->color);
-             nxbe_fill(&fe.be.bkgd, &fe.be.bkgd.bounds, bgcolormsg->color);
+             FAR struct nxsvrmsg_setbgcolor_s *bgcolormsg =
+               (FAR struct nxsvrmsg_setbgcolor_s *)buffer;
+
+             /* Has the background color changed? */
+
+             if (!nxgl_colorcmp(fe.be.bgcolor, bgcolormsg->color))
+               {
+                 /* Yes.. fill the background */
+
+                 nxgl_colorcopy(fe.be.bgcolor, bgcolormsg->color);
+                 nxbe_fill(&fe.be.bkgd, &fe.be.bkgd.bounds, bgcolormsg->color);
+               }
            }
            break;
 

graphics/nxsu/nx_setbgcolor.c

@@ -97,7 +97,15 @@ int nx_setbgcolor(NXHANDLE handle,
     }
 #endif
 
-  nxgl_colorcopy(fe->be.bgcolor, color);
-  nxbe_fill(&fe->be.bkgd, &fe->be.bkgd.bounds, color);
+  /* Has the background color changed? */
+
+  if (!nxgl_colorcmp(fe.be.bgcolor, bgcolormsg->color))
+    {
+      /* Yes.. fill the background */
+
+      nxgl_colorcopy(fe->be.bgcolor, color);
+      nxbe_fill(&fe->be.bkgd, &fe->be.bkgd.bounds, color);
+    }
+
   return OK;
 }