[PATCH v2] git-gui: use gray background for inactive text widgets

[Stefan Haller <stefan@haller-berlin.de>]

Second version; it simplifies the code to initialize and update the colors in
the two file list views a bit, and it calculates a gray color for the inactive
selection from the active selection. This looks a lot better in the themes I
have tried.

The bug with the inactive diff selection background on Mac is still there,
however.

--- 8< ---

This makes it easier to see at a glance which of the four main views has the
keyboard focus.
---
 git-gui.sh     | 18 ++++++++++++------
 lib/themed.tcl | 21 +++++++++++++++++----
 2 files changed, 29 insertions(+), 10 deletions(-)

diff --git a/git-gui.sh b/git-gui.sh
index 867b8ce..e818caa 100755
--- a/git-gui.sh
+++ b/git-gui.sh
@@ -720,9 +720,6 @@ proc rmsel_tag {text} {
 		-background [$text cget -background] \
 		-foreground [$text cget -foreground] \
 		-borderwidth 0
-	$text tag conf in_sel\
-		-background $color::select_bg \
-		-foreground $color::select_fg
 	bind $text <Motion> break
 	return $text
 }
@@ -3322,11 +3319,20 @@ if {!$use_ttk} {
 	.vpane.files paneconfigure .vpane.files.index -sticky news
 }

+proc set_selection_colors {w has_focus} {
+	foreach tag [list in_diff in_sel] {
+		$w tag conf $tag \
+			-background [expr {$has_focus ? $color::select_bg : $color::inactive_select_bg}] \
+			-foreground [expr {$has_focus ? $color::select_fg : $color::inactive_select_fg}]
+	}
+}
+
 foreach i [list $ui_index $ui_workdir] {
 	rmsel_tag $i
-	$i tag conf in_diff \
-		-background $color::select_bg \
-		-foreground $color::select_fg
+
+	set_selection_colors $i 0
+	bind $i <FocusIn>	{ set_selection_colors %W 1 }
+	bind $i <FocusOut>	{ set_selection_colors %W 0 }
 }
 unset i

diff --git a/lib/themed.tcl b/lib/themed.tcl
index eda5f8c..db49085 100644
--- a/lib/themed.tcl
+++ b/lib/themed.tcl
@@ -6,8 +6,10 @@ namespace eval color {
 	# Variable colors
 	# Preffered way to set widget colors is using add_option.
 	# In some cases, like with tags in_diff/in_sel, we use these colors.
-	variable select_bg		lightgray
-	variable select_fg		black
+	variable select_bg				lightgray
+	variable select_fg				black
+	variable inactive_select_bg		lightgray
+	variable inactive_select_fg		black

 	proc sync_with_theme {} {
 		set base_bg		[ttk::style lookup . -background]
@@ -19,6 +21,8 @@ namespace eval color {

 		set color::select_bg $select_bg
 		set color::select_fg $select_fg
+		set color::inactive_select_bg [convert_rgb_to_gray $select_bg]
+		set color::inactive_select_fg $select_fg

 		proc add_option {key val} {
 			option add $key $val widgetDefault
@@ -36,11 +40,20 @@ namespace eval color {
 		add_option *Text.Foreground $text_fg
 		add_option *Text.selectBackground $select_bg
 		add_option *Text.selectForeground $select_fg
-		add_option *Text.inactiveSelectBackground $select_bg
-		add_option *Text.inactiveSelectForeground $select_fg
+		add_option *Text.inactiveSelectBackground $color::inactive_select_bg
+		add_option *Text.inactiveSelectForeground $color::inactive_select_fg
 	}
 }

+proc convert_rgb_to_gray {rgb} {
+	# Simply take the average of red, green and blue. This wouldn't be good
+	# enough for, say, converting a photo to grayscale, but for this simple
+	# purpose of approximating the brightness of a color it's good enough.
+	lassign [winfo rgb . $rgb] r g b
+	set gray [expr {($r / 256 + $g / 256 + $b / 256) / 3}]
+	return [format "#%2.2X%2.2X%2.2X" $gray $gray $gray]
+}
+
 proc ttk_get_current_theme {} {
 	# Handle either current Tk or older versions of 8.5
 	if {[catch {set theme [ttk::style theme use]}]} {
--
2.29.0.21.g59e7d82785.dirty