gitk: scrolling updates for TclTk 8.7+ / TIP474

TclTk 8.7 (still in alpha), and 9.0 (released), implement TIP 474 that
delivers uniform handling of mouse and touchpad scrolling events on all
platforms, and by default bound to most widgets. This means that gitk
needs specific bindings only for scrolling the top 3 panes and can use
the same bindings on all platforms.

TIP 474 provides the delta (%D) value as nominally 120 for a single
wheel click, but can be smaller for fine motion. Shift- events are used
for horizontal scrolling, and both are connected for the mouse wheel and
for touchpads. Also the Option- modifier (the Alt key on PCs, the Option
key on Macs) is used to select large rather than fine motion.  Button
events are never used.

This largely follows the prior win32 model, except that Tk 8.6 does not
reliably use the Option- modifier because the Alt- key conflicts with
builtin behavior to activate the main menubar. Presumably this conflict
is addressed in the win32 Tcl9.x package. So, create a new Tcl9 mouse
binding set, based upon win32, but adding Option- bindings that increase
scrolling motion by a factor of 5, in keeping with the basic Tk 9.x
behavior.

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

Author: mark987

gitk

@@ -2681,7 +2681,22 @@ proc makewindow {} {
     pack .ctop -fill both -expand 1
     bindall <1> {selcanvline %W %x %y}
     #Mouse / touchpad scrolling
-    if {[tk windowingsystem] == "win32"} {
+    if {[package vcompare $::tcl_version 8.7] >= 0} {
+        bindall <MouseWheel> {allcanvs yview scroll [expr -%D*$kscroll/120.] units}
+        bindall <Shift-MouseWheel> break
+        bind $ctext <MouseWheel> {$ctext yview scroll [expr -%D*$kscroll/120.] units}
+        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*$kscroll/120.] units}
+        bindall <Alt-MouseWheel> {allcanvs yview scroll [expr -%D*$kscroll/24.] units}
+        bindall <Alt-Shift-MouseWheel> break
+        bind $ctext <Alt-MouseWheel> {$ctext yview scroll [expr -%D*$kscroll/24.] units}
+        bind $ctext <Alt-Shift-MouseWheel> {$ctext xview scroll [expr -%D*$kscroll/24.] units}
+        bind $cflist <Alt-MouseWheel> {$cflist yview scroll [expr -%D*$kscroll/24.] units}
+        bind $cflist <Alt-Shift-MouseWheel> {$cflist xview scroll [expr -%D*$kscroll/24.] units}
+        bind $canv <Alt-Shift-MouseWheel> {$canv xview scroll [expr -%D*$kscroll/24.] units}
+    } elseif {[tk windowingsystem] == "win32"} {
         bindall <MouseWheel> {allcanvs yview scroll [expr -%D*$kscroll/120] units}
         bindall <Shift-MouseWheel> break
         bind $ctext <MouseWheel> {$ctext yview scroll [expr -%D*$kscroll/120] units}