Improve Button appearance. Fix Label bug where value too long.

README.md

@@ -53,11 +53,15 @@ Code is new and issues are likely: please report any found. This document is
 under review. I plan to add further demos and to upgrade the performance of
 some display drivers.
 
+An issue under investigation is that a soft reset is required after a GUI
+application is run and before running another. Otherwise the second application
+displays correctly but is unresponsive.
+
 # 0. Contents
 
 1. [Basic concepts](./README.md#1-basic-concepts) Including installation and test.  
  1.1 [Coordinates](./README.md#11-coordinates) The GUI's coordinate system.  
- 1.2 [Screen Window and Widget objects](./README.md#12-Screen-window-and-widget-objects)  
+ 1.2 [Screen Window and Widget objects](./README.md#12-Screen-window-and-widget-objects) Basic GUI classes.  
  1.3 [Fonts](./README.md#13-fonts)  
  1.4 [Navigation](./README.md#14-navigation) How the GUI navigates between widgets.  
  1.5 [Hardware definition](./README.md#15-hardware-definition) How to configure your hardware.  
@@ -396,9 +400,11 @@ minimal and aim to demonstrate a single technique.
  * `slider.py` A `Slider` whose color varies with its value.
  * `slider_label.py` A `Slider` updating a `Label`. Good for trying precision
  mode.
- * `linked_slider.py` One slider updating two others, and a coding "wrinkle"
+ * `linked_slider.py` One `Slider` updating two others, and a coding "wrinkle"
  required for doing this.
- * `screen_change.py` A `Pushbutton` causing a screen change.
+ * `dialog.py` `DialogBox` demo. Illustrates the screen change mechanism.
+ * `screen_change.py` A `Pushbutton` causing a screen change using a re-usable
+ "forward" button.
  * `tbox.py` Text boxes and user-controlled scrolling.
 
 ### 1.11.2 Test scripts
@@ -643,10 +649,6 @@ In normal use the following methods only are required:
  passing positional and keyword arguments to the constructor of the new, user
  defined, screen.
  * `back(cls)` Restore previous screen.
- * `value(cls, val=None)` The `val` arg can be any Python type. It allows
- widgets on a `Screen` to store information in a way which can be accessed from
- the calling screen. This typically occurs after the screen has closed and no
- longer exists as an instance, hence the use of a classmethod.
 
 These are uncommon:__
  * `shutdown(cls)` Clear the screen and shut down the GUI. Normally done by a

gui/core/ugui.py

@@ -202,15 +202,6 @@ class Display:
 class Screen:
     current_screen = None
     is_shutdown = Event()
-    _value = None
-
-    # Allow a Screen to store an arbitrary object. Retrieval may be
-    # done by caller, after the Screen instance was deleted
-    @classmethod
-    def value(cls, val=None):
-        if val is not None:
-            cls._value = val
-        return cls._value
 
     @classmethod
     def next_ctrl(cls):
@@ -490,9 +481,19 @@ class Screen:
             gc.threshold(gc.mem_free() // 4 + gc.mem_alloc())
             #print(gc.mem_free())
 
-# Very basic window class. Cuts a rectangular hole in a screen on which content may be drawn
+# Very basic window class. Cuts a rectangular hole in a screen on which
+# content may be drawn.
 class Window(Screen):
 
+    _value = None
+    # Allow a Window to store an arbitrary object. Retrieval may be
+    # done by caller, after the Window instance was deleted
+    @classmethod
+    def value(cls, val=None):
+        if val is not None:
+            cls._value = val
+        return cls._value
+
     def __init__(self, row, col, height, width, *, draw_border=True, bgcolor=None, fgcolor=None):
         Screen.__init__(self)
         self.row = row

gui/core/writer.py

@@ -264,7 +264,7 @@ class Writer():
     def setcolor(self, *_):
         return self.fgcolor, self.bgcolor
 
-# Writer for colour displays or upside down rendering
+# Writer for colour displays
 class CWriter(Writer):
 
 

gui/widgets/buttons.py

@@ -21,7 +21,7 @@ class Button(Widget):
             width = max(sl, height)
             height = width
         else:
-            width = max(sl, width)
+            width = max(sl + 10, width)  # Allow 5 pixels before and after text
         super().__init__(writer, row, col, height, width, fgcolor, bgcolor, bdcolor, False, True)
         self.shape = shape
         self.radius = height // 2
@@ -100,9 +100,9 @@ class Button(Widget):
 class CloseButton(Button):
     def __init__(self, writer, width=0, callback=dolittle, args=(), bgcolor=RED):
         scr = Screen.current_screen
-        # The factor of 2 is an empirical fix to make it look OK over
-        # the range of fonts in use.
-        wd = width if width else writer.stringlen('X') * 2
+        # Calculate the button width if not provided. Button allows
+        # 5 pixels either side.
+        wd = width if width else (writer.stringlen('X') + 10)
         self.user_cb = callback
         self.user_args = args
         super().__init__(writer, *scr.locn(4, scr.width - wd - 4),

gui/widgets/dialog.py

@@ -25,7 +25,7 @@ class DialogBox(Window):
 
         height = 80
         spacing = 10
-        buttonwidth = max(max(writer.stringlen(e[0]) for e in elements) + 4, buttonwidth)
+        buttonwidth = max(max(writer.stringlen(e[0]) for e in elements) + 14, buttonwidth)
         buttonheight = max(writer.height, 15)
         nelements = len(elements)
         width = spacing + (buttonwidth + spacing) * nelements

gui/widgets/label.py

@@ -9,6 +9,7 @@ from gui.core.colors import *
 # text: str display string int save width
 class Label(Widget):
     def __init__(self, writer, row, col, text, invert=False, fgcolor=None, bgcolor=BLACK, bdcolor=False):
+        self.writer = writer
         # Determine width of object
         if isinstance(text, int):
             width = text
@@ -22,6 +23,8 @@ class Label(Widget):
             self.value(text, invert)
 
     def value(self, text=None, invert=False, fgcolor=None, bgcolor=None, bdcolor=None):
+        if self.writer.stringlen(text) > self.width:
+            raise ValueError('Label.value() string is too long.')
         txt = super().value(text)  # Sets .draw ensuring refresh
         # Redraw even if no text supplied: colors may have changed.
         self.invert = invert