render: When grid fitting independent axis, at least fit in the same direction

Author: terryburton

src/render.ps.src

@@ -900,6 +900,11 @@ begin
         %
         1 0 gridmatrix dtransform abs exch abs 2 copy lt {exch} if pop
 
+        % Snap mode used for x (0=round, 1=floor, 2=ceiling). The snapy
+        % branch replays this against the y-axis devpx so square matrix
+        % symbols stay square when the x-axis retry bumps to floor/ceiling.
+        /xsnapmode 0 def
+
         xdim 0 ne {  % strictspec is provided
             /devpx exch def
             /snapped devpx 0 snapto def
@@ -908,6 +913,7 @@ begin
                 pop pop  % Discard error details
                 /snap1 snapped def
                 devpx mag div dup floor sub 0.5 lt { 2 } { 1 } ifelse
+                dup /xsnapmode exch def
                 devpx exch snapto /snapped exch def
                 snapped effx xmin xmax //render.validate_xdim exec
                 not {
@@ -921,7 +927,7 @@ begin
                             xmax -1 ne { 1 index xmax sub dup 0 gt { add } { pop } ifelse } if
                             exch pop
                         } def
-                        eff1 dist eff2 dist lt { /snapped snap1 def } if
+                        eff1 dist eff2 dist lt { /snapped snap1 def /xsnapmode 0 def } if
                     } {
                         /bwipp.renderGridfitXdimOutOfSpec
                         [ (No X-dimension within the permissible range )
@@ -941,7 +947,7 @@ begin
 
         snapy {
             0 1 gridmatrix dtransform abs exch abs 2 copy lt {exch} if pop
-            dup mag div round dup 0 le { pop 1 } if mag mul exch div
+            dup xsnapmode snapto exch div
         } { dup } ifelse
 
         scale

tests/ps_tests/rendergridfit.ps.test

@@ -63,3 +63,44 @@
 { gsave 0 0 moveto 10 dict begin /loosespec false def /griddpi 300 def 1 0.330 0.3295 0.3305 false false /gridfit render end
   not { pop grestore } if  % Discard info string, grestore
 } /bwipp.renderGridfitXdimOutOfSpec isEqual
+
+%
+% snapy=true must mirror the x-axis retry direction so square matrix
+% symbols (QR, Data Matrix, Aztec, ...) stay square.  The three cases
+% below exercise each xsnapmode outcome and assert scale_x == scale_y
+% by comparing |dtransform(1,0)| against |dtransform(0,1)| after gridfit.
+% Dev-px calculations assume the test device's 72 DPI resolution so
+% devpx = griddpi / 72 per user unit.
+%
+% snapy=true + ceiling retry (xsnapmode=2)
+% griddpi=300: devpx=4.167, round=4 eff=0.288 < xmin=0.295, frac=0.167 <0.5
+% so retry picks ceiling=5 eff=0.360 within [0.295, 0.400].  y must
+% also snap to 5 rather than its independent round=4.
+%
+{ gsave 0 0 moveto 10 dict begin /loosespec false def /griddpi 300 def 1 0.300 0.295 0.400 false true /gridfit render
+  { 1 0 dtransform abs exch abs add 0 1 dtransform abs exch abs add sub abs 0.0001 lt }
+  { pop false } ifelse
+  end grestore } true isEqual
+
+%
+% snapy=true + floor retry (xsnapmode=1)
+% griddpi=200: devpx=2.778, round=3 eff=0.410 > xmax=0.379, frac=0.778 >=0.5
+% so retry picks floor=2 eff=0.274 within [0.200, 0.379].  y must
+% also snap to 2 rather than its independent round=3.
+%
+{ gsave 0 0 moveto 10 dict begin /loosespec false def /griddpi 200 def 1 0.380 0.200 0.379 false true /gridfit render
+  { 1 0 dtransform abs exch abs add 0 1 dtransform abs exch abs add sub abs 0.0001 lt }
+  { pop false } ifelse
+  end grestore } true isEqual
+
+%
+% snapy=true + loosespec revert to snap1 (xsnapmode reset to 0)
+% griddpi=300: devpx=4.167, round=4 eff=0.288 < xmin=0.295 fail,
+% retry ceiling=5 eff=0.360 > xmax=0.350 fail.  loosespec picks closer:
+% dist(0.288)=0.007 < dist(0.360)=0.010, so snap1 (round=4) wins and
+% xsnapmode must reset to 0 so y also rounds to 4, not stay at ceil=5.
+%
+{ gsave 0 0 moveto 10 dict begin /loosespec true def /griddpi 300 def 1 0.300 0.295 0.350 false true /gridfit render
+  { 1 0 dtransform abs exch abs add 0 1 dtransform abs exch abs add sub abs 0.0001 lt }
+  { pop false } ifelse
+  end grestore } true isEqual