[FREELDR:UI] Improve drawing of progress bars, reducing flickering.

- Remove excessive UiDrawBackdrop() calls that caused too many
  unnecessary redraws.

- ProgressBar: Clear only the portions that need to be cleared up.
  This allows to not use DrawBackdrop anymore and the flickering.

boot/freeldr/freeldr/disk/ramdisk.c

@@ -117,7 +117,6 @@ RamDiskLoadVirtualFile(
     LARGE_INTEGER Position;
 
     /* Display progress */
-    UiDrawBackdrop();
     UiDrawProgressBarCenter(1, 100, MsgBuffer);
 
     /* Try opening the Ramdisk file */

boot/freeldr/freeldr/ntldr/setupldr.c

@@ -490,9 +490,8 @@ LoadReactOSSetup(
         return EINVAL;
     }
 
-    UiDrawStatusText("Setup is loading...");
-
     UiDrawBackdrop();
+    UiDrawStatusText("Setup is loading...");
     UiDrawProgressBarCenter(1, 100, "Loading ReactOS Setup...");
 
     /* Retrieve the system path */
@@ -738,7 +737,6 @@ LoadReactOSSetup(
     SetupBlock->Flags = SETUPLDR_TEXT_MODE;
 
     /* Load the "setupreg.hiv" setup system hive */
-    UiDrawBackdrop();
     UiDrawProgressBarCenter(15, 100, "Loading setup system hive...");
     Success = WinLdrInitSystemHive(LoaderBlock, BootPath, TRUE);
     TRACE("Setup SYSTEM hive %s\n", (Success ? "loaded" : "not loaded"));

boot/freeldr/freeldr/ntldr/winldr.c

@@ -382,7 +382,6 @@ WinLdrLoadModule(PCSTR ModuleName,
     //CHAR ProgressString[256];
 
     /* Inform user we are loading files */
-    //UiDrawBackdrop();
     //RtlStringCbPrintfA(ProgressString, sizeof(ProgressString), "Loading %s...", FileName);
     //UiDrawProgressBarCenter(1, 100, ProgressString);
 
@@ -467,7 +466,6 @@ LoadModule(
     CHAR ProgressString[256];
     PVOID BaseAddress = NULL;
 
-    UiDrawBackdrop();
     RtlStringCbPrintfA(ProgressString, sizeof(ProgressString), "Loading %s...", File);
     UiDrawProgressBarCenter(Percentage, 100, ProgressString);
 
@@ -918,7 +916,6 @@ LoadAndBootWindows(
     AllocateAndInitLPB(OperatingSystemVersion, &LoaderBlock);
 
     /* Load the system hive */
-    UiDrawBackdrop();
     UiDrawProgressBarCenter(15, 100, "Loading system hive...");
     Success = WinLdrInitSystemHive(LoaderBlock, BootPath, FALSE);
     TRACE("SYSTEM hive %s\n", (Success ? "loaded" : "not loaded"));
@@ -977,7 +974,6 @@ LoadAndBootWindowsCommon(
     SystemRoot = strstr(BootPath, "\\");
 
     /* Detect hardware */
-    UiDrawBackdrop();
     UiDrawProgressBarCenter(20, 100, "Detecting hardware...");
     LoaderBlock->ConfigurationRoot = MachHwDetect();
 
@@ -994,7 +990,6 @@ LoadAndBootWindowsCommon(
     }
 
     /* Load boot drivers */
-    UiDrawBackdrop();
     UiDrawProgressBarCenter(100, 100, "Loading boot drivers...");
     Success = WinLdrLoadBootDrivers(LoaderBlock, BootPath);
     TRACE("Boot drivers loading %s\n", Success ? "successful" : "failed");

boot/freeldr/freeldr/ui/minitui.c

@@ -80,6 +80,15 @@ MiniTuiDrawProgressBar(
     /* First make sure the progress bar text fits */
     UiTruncateStringEllipsis(ProgressText, ProgressBarWidth);
 
+    /* Clear the text area */
+    TuiFillArea(Left, Top, Right,
+#ifdef NTLDR_PROGRESSBAR
+                Bottom - 1,
+#else // BTMGR_PROGRESSBAR
+                Bottom - 2, // One empty line between text and bar.
+#endif
+                ' ', ATTR(UiTextColor, UiMenuBgColor));
+
     /* Draw the "Loading..." text */
     TuiDrawCenteredText(Left, Top, Right,
 #ifdef NTLDR_PROGRESSBAR
@@ -89,13 +98,15 @@ MiniTuiDrawProgressBar(
 #endif
                         ProgressText, ATTR(UiTextColor, UiMenuBgColor));
 
-    /* Draw the percent complete */
+    /* Draw the percent complete -- Use the fill character */
     for (i = 0; i < (Position * ProgressBarWidth) / Range; i++)
     {
-        /* Use the fill character */
         TuiDrawText(Left + i, Bottom,
                     "\xDB", ATTR(UiTextColor, UiMenuBgColor));
     }
+    /* Fill the remaining with blanks */
+    TuiFillArea(Left + i, Bottom, Right, Bottom,
+                ' ', ATTR(UiTextColor, UiMenuBgColor));
 
 #ifndef _M_ARM
     TuiUpdateDateTime();

boot/freeldr/freeldr/ui/tui.c

@@ -744,20 +744,15 @@ TuiDrawProgressBar(
     TuiDrawCenteredText(Left, Top, Right, Bottom - 1,
                         ProgressText, ATTR(UiTextColor, UiMenuBgColor));
 
-    /* Draw the percent complete */
+    /* Draw the percent complete -- Use the fill character */
     for (i = 0; i < (Position * ProgressBarWidth) / Range; i++)
     {
-        /* Use the fill character */
         TuiDrawText(Left + i, Bottom,
                     "\xDB", ATTR(UiTextColor, UiMenuBgColor));
     }
-
-    /* Draw the shadow */
-    for (; i < ProgressBarWidth; i++)
-    {
-        TuiDrawText(Left + i, Bottom,
-                    "\xB2", ATTR(UiTextColor, UiMenuBgColor));
-    }
+    /* Fill the remaining with shadow blanks */
+    TuiFillArea(Left + i, Bottom, Right, Bottom,
+                '\xB2', ATTR(UiTextColor, UiMenuBgColor));
 
 #ifndef _M_ARM
     TuiUpdateDateTime();