Auto-show the text window when stepping a dimension, in addition to

auto-showing when a solve fails. And accept expressions, not just
numbers, for that new dimension value.

[git-p4: depot-paths = "//depot/solvespace/": change = 1877]

draw.cpp

@@ -924,10 +924,8 @@ void GraphicsWindow::Paint(int w, int h) {
     } else {
         // Draw a red background whenever we're having solve problems.
         glClearColor(0.4f, 0, 0, 1.0f);
-        if(!showTextWindow) {
-            showTextWindow = true;
-            ShowTextWindow(TRUE);
-        }
+        // And show the text window, which has info to debug it
+        ForceTextWindowShown();
     }
 
     glClearDepth(1.0); 

graphicswin.cpp

@@ -430,6 +430,14 @@ bool GraphicsWindow::LockedInWorkplane(void) {
     return (SS.GW.ActiveWorkplane().v != Entity::FREE_IN_3D.v);
 }
 
+void GraphicsWindow::ForceTextWindowShown(void) {
+    if(!showTextWindow) {
+        showTextWindow = true;
+        CheckMenuById(MNU_SHOW_TEXT_WND, true);
+        ShowTextWindow(TRUE);
+    }
+}
+
 void GraphicsWindow::MenuEdit(int id) {
     switch(id) {
         case MNU_UNSELECT_ALL:

solvespace.cpp

@@ -373,6 +373,10 @@ void SolveSpace::MenuAnalyze(int id) {
                     SS.TW.shown.constraint = c->h;
                     SS.TW.shown.screen = TextWindow::SCREEN_STEP_DIMENSION;
 
+                    // The step params are specified in the text window,
+                    // so force that to be shown.
+                    SS.GW.ForceTextWindowShown();
+
                     SS.later.showTW = true;
                     SS.GW.ClearSelection();
                 } else {

textscreens.cpp

@@ -929,13 +929,19 @@ void TextWindow::EditControlDone(char *s) {
             break;
         }
 
-        case EDIT_STEP_DIM_FINISH:
+        case EDIT_STEP_DIM_FINISH: {
+            Expr *e = Expr::From(s);
+            if(!e) {
+                Error("Not a valid number or expression: '%s'", s);
+                break;
+            }
             if(shown.dimIsDistance) {
-                shown.dimFinish = SS.StringToMm(s);
+                shown.dimFinish = SS.ExprToMm(e);
             } else {
-                shown.dimFinish = atof(s);
+                shown.dimFinish = e->Eval();
             }
             break;
+        }
 
         case EDIT_STEP_DIM_STEPS:
             shown.dimSteps = min(300, max(1, atoi(s)));

ui.h

@@ -292,6 +292,7 @@ public:
     bool LockedInWorkplane(void);
     void SetWorkplaneFreeIn3d(void);
     hEntity ActiveWorkplane(void);
+    void ForceTextWindowShown(void);
 
     // Operations that must be completed by doing something with the mouse
     // are noted here. These occupy the same space as the menu ids.