From a2368f803f45f33f403e122428b9b493ca458986 Mon Sep 17 00:00:00 2001
From: Ian Jackson <ian@liberator.relativity.greenend.org.uk>
Date: Sun, 8 Aug 2010 18:44:50 +0100
Subject: [PATCH] where-vessels: more fine-grained scale-selection

---
 yarrg/where-vessels | 37 ++++++++++++++++++++++++++-----------
 1 file changed, 26 insertions(+), 11 deletions(-)

diff --git a/yarrg/where-vessels b/yarrg/where-vessels
index f4fee80..4e6a225 100755
--- a/yarrg/where-vessels
+++ b/yarrg/where-vessels
@@ -952,8 +952,18 @@ proc load-chart {} {
     }]]
 }
 
-
-set scale 16
+proc init-scales {} {
+    global scales scaleix scale
+    set defscale 16
+    set scales {1 2 3 4 5 6 8}
+    set e12 {10 12 15 18 22 27 33 39 47 56 68 82}
+    foreach t $e12 {
+	if {$t < $defscale} { set scaleix [llength $scales] }
+	lappend scales $t
+    }
+    foreach t [lrange $e12 0 6] { lappend scales [expr {$t * 10}] }
+    set scale [lindex $scales $scaleix]
+}
 
 proc coord {c} {
 	global scale
@@ -1289,9 +1299,11 @@ proc widgets-setup {} {
     frame .cp.ctrl.zoom
     pack .cp.ctrl.zoom -side top
 
-    button .cp.ctrl.zoom.out -text - -font {Courier 16} -command {zoom /2} -pady 0
-    button .cp.ctrl.zoom.in  -text + -font {Courier 16} -command {zoom *2} -pady 0
-    pack .cp.ctrl.zoom.out .cp.ctrl.zoom.in -side left
+    foreach inout {out in} minplus {- +} {
+	button .cp.ctrl.zoom.$inout -text $minplus -font {Courier 16} \
+	    -command "zoom ${minplus}1" -pady 0
+	pack .cp.ctrl.zoom.$inout -side left
+    }
 
     parser-control-create .cp.ctrl.acquire \
 	acquire Acquire \
@@ -1380,12 +1392,14 @@ proc show-report {islandname code} {
     }
 }
 
-proc zoom {extail} {
-    global scale canvas
-    set nscale [expr "\$scale $extail"]
-    debug "ZOOM $scale $nscale"
-    if {$nscale < 1 || $nscale > 200} return
-    set scale $nscale
+proc zoom {amt} {
+    global scaleix scales scale canvas
+    incr scaleix $amt
+    if {$scaleix < 0} { set scaleix 0 }
+    set nscales [llength $scales]
+    if {$scaleix >= $nscales} { set scaleix [expr {$nscales-1}] }
+    set scale [lindex $scales $scaleix]
+    debug "ZOOM $amt $scaleix $scale"
     draw
 }
 
@@ -1434,6 +1448,7 @@ proc invoke_notes {} {
 
 #---------- main program ----------
 
+init-scales
 parseargs
 argdefaults
 httpclientsetup where-vessels
-- 
2.30.2