add MessageScreen back and tweak/enhance screen layouts

this will be used for a help screen, which isn't done yet, but this
makes the edit screen incrementally better too

Signed-off-by: Brian S. Stephan <bss@incorporeal.org>

gp2040ce_bintools/config_tree.css

@@ -5,12 +5,12 @@ Tree {
 Button {
     border: round gray;
     content-align: center middle;
-    width: 100%;
+    max-width: 50%;
     height: 100%;
     margin: 0 1;
 }
 
-EditScreen {
+EditScreen, MessageScreen {
     align: center middle;
 }
 
@@ -31,14 +31,25 @@ EditScreen Label {
 }
 
 #edit-dialog {
-    grid-size: 2;
-    grid-rows: 1fr 3fr 1fr 2fr;
     padding: 0 1;
+    grid-rows: 1fr 1fr 1fr 1fr;
     width: 50%;
     height: 50%;
     border: tall gray 100%;
 }
 
+#message-dialog {
+    padding: 0 1;
+    grid-rows: 3fr 1fr;
+    width: 50%;
+    height: 50%;
+    border: tall gray 100%;
+}
+
+#button-container {
+    align: right middle;
+}
+
 #field-name, #field-input, #input-errors {
     column-span: 2;
 }

gp2040ce_bintools/gui.py

@@ -12,7 +12,7 @@ from rich.highlighter import ReprHighlighter
 from rich.text import Text
 from textual import on
 from textual.app import App, ComposeResult
-from textual.containers import Grid
+from textual.containers import Container, Grid, Horizontal
 from textual.logging import TextualHandler
 from textual.screen import ModalScreen
 from textual.validation import Number
@@ -57,11 +57,12 @@ class EditScreen(ModalScreen):
             # we don't handle whatever these are yet
             self.input_field = Label(repr(self.field_value), id='field-input')
         yield Grid(
-            Label(self.field_descriptor.full_name, id="field-name"),
-            self.input_field,
-            Pretty('', id='input-errors', classes='hidden'),
-            Button("Confirm", id='confirm-button'),
-            Button("Cancel", id='cancel-button'),
+            Container(Label(self.field_descriptor.full_name, id="field-name"), id="field-name-container"),
+            Container(self.input_field, id="input-field-container"),
+            Container(Pretty('', id='input-errors', classes='hidden'), id="error-container"),
+            Horizontal(Button("Confirm", id='confirm-button'),
+                       Button("Cancel", id='cancel-button'),
+                       id="button-container"),
             id='edit-dialog',
         )
 
@@ -102,6 +103,27 @@ class EditScreen(ModalScreen):
             self.node.set_label(pb_field_to_node_label(self.field_descriptor, field_value))
 
 
+class MessageScreen(ModalScreen):
+    """Simple screen for displaying messages."""
+
+    def __init__(self, text: str, *args, **kwargs):
+        """Store the message for later display."""
+        self.text = text
+        super().__init__(*args, **kwargs)
+
+    def compose(self) -> ComposeResult:
+        """Build the pop-up window with the desired message displayed."""
+        yield Grid(
+            Container(Label(self.text, id="message-text"), id="text-container"),
+            Container(Button("OK", id='ok-button'), id="button-container"),
+            id='message-dialog',
+        )
+
+    def on_button_pressed(self, event: Button.Pressed) -> None:
+        """Process the button action (close the window)."""
+        self.app.pop_screen()
+
+
 class ConfigEditor(App):
     """Display the GP2040-CE configuration as a tree."""