gitk: commit-graph x-scrolling on all platforms

Since 5fdcbb1 ("gitk: Fixes for Mac OS X TkAqua", 2009-03-23), gitk
provides horizontal scrolling of the commit graph pane on aqua, but not
on x11 or win32. Also, the horizontal scrolling is triggered by mouse
events attached to any of the three panes, not just the commit graph
that is the only one that scrolls. It is unusual to scroll a widget that
is not under the mouse, many would consider this a bug. Also, no
horizontal scrollbar is provided for this, so there is no real cue for
the user that horizontal scrolling is available. A prior commit removed
this aqua only feature.

Let's connect this as a feature on all platforms, and use the
transmitted delta (%D) value and the user preference kscroll to adjust
the amount scrolled for aqua and win32. x11 receives only button events,
so uses $kscroll alone for the scrolling value. For horizontal
scrolling, honor only events received by the commit graph in conformance
with normal GUI design.  Vertical scrolling is unchanged, and events
received by any of the 3 panes continue to scroll all 3 in unison.

Vertical scrolling is already scaled by the vertical font size metrics,
this is a suitable value to scale the horizontal scrolling as well.

Per the ancient and long ignored CUA standards, we should add a
horizontal scrollbar to the commit-graph, but gitk's interface is
already very cluttered: adding a scrollbar to only one of these three
panes is difficult while maintaining common pane vertical size,
especially so considering the movable sash separating panes 1 & 2, and
will consume yet more space. So, leave this as a hidden feature, now
available on all platforms.

Signed-off-by: Mark Levedahl <[email protected]>

Author: mark987

gitk

@@ -2302,6 +2302,7 @@ proc makewindow {} {
     canvas $canv \
         -selectbackground $selectbgcolor \
         -background $bgcolor -bd 0 \
+        -xscrollincr $linespc \
         -yscrollincr $linespc -yscrollcommand "scrollcanv $cscroll"
     .tf.histframe.pwclist add $canv
     set canv2 .tf.histframe.pwclist.canv2
@@ -2687,6 +2688,7 @@ proc makewindow {} {
         bind $ctext <Shift-MouseWheel> {$ctext xview scroll [expr -%D*$kscroll/120] units}
         bind $cflist <MouseWheel> {$cflist yview scroll [expr -%D*$kscroll/120] units}
         bind $cflist <Shift-MouseWheel> {$cflist xview scroll [expr -%D*$kscroll/120] units}
+        bind $canv <Shift-MouseWheel> {$canv xview scroll [expr -%D*$kscroll/120] units}
     } elseif {[tk windowingsystem] == "x11"} {
         bindall <ButtonRelease-4> {allcanvs yview scroll -$kscroll units}
         bindall <ButtonRelease-5> {allcanvs yview scroll $kscroll units}
@@ -2700,13 +2702,16 @@ proc makewindow {} {
         bind $cflist <ButtonRelease-5> {$cflist yview scroll  $kscroll units}
         bind $cflist <Shift-ButtonRelease-4> {$cflist xview scroll -$kscroll units}
         bind $cflist <Shift-ButtonRelease-5> {$cflist xview scroll  $kscroll units}
+        bind $canv <Shift-ButtonRelease-4> {$canv xview scroll -$kscroll units}
+        bind $canv <Shift-ButtonRelease-5> {$canv xview scroll  $kscroll units}
     } elseif {[tk windowingsystem] == "aqua"} {
         bindall <MouseWheel> {allcanvs yview scroll [expr -%D*$kscroll] units}
         bindall <Shift-MouseWheel> break
         bind $ctext <MouseWheel> {$ctext yview scroll [expr -%D*$kscroll] units}
         bind $ctext <Shift-MouseWheel> {$ctext xview scroll [expr -%D*$kscroll] units}
         bind $cflist <MouseWheel> {$cflist yview scroll [expr -%D*$kscroll] units}
         bind $cflist <Shift-MouseWheel> {$cflist xview scroll [expr -%D*$kscroll] units}
+        bind $canv <Shift-MouseWheel> {$canv xview scroll [expr -%D*$kscroll] units}
     } else {
         puts stderr "Unknown windowing system, cannot bind mouse"
     }