Add fullscreen in-app image view, no stretch, sharing the editor's in-app/external toggle

Editor.py

@@ -0,0 +1,160 @@
+"""In-app text/config/markup viewer and editor (Features/Major: "Different
+display in middle" — the code-editor part). Fills Browser's file-area
+Container in place of the entry list while a file is open.
+
+Flet 1.0.1 has no CodeMirror-equivalent rich editor widget and no embeddable
+WebView, so this mirrors SaraView's View/Edit split as closely as Flet
+actually allows: View mode gets real syntax highlighting by wrapping the
+content in a fenced code block and rendering it read-only via ft.Markdown
+(which ships GitHub-style highlight.js theming); Edit mode is a plain
+monospace TextField — no highlighting while typing — with an explicit Save."""
+
+import re
+from pathlib import Path
+from typing import Callable, Optional
+
+import flet as ft
+
+from Core import ChipButtonStyle, Palette
+
+LanguageByExtension = {
+    ".py": "python", ".json": "json", ".toml": "toml", ".yaml": "yaml", ".yml": "yaml",
+    ".js": "javascript", ".ts": "typescript", ".css": "css", ".html": "xml", ".htm": "xml",
+    ".xml": "xml", ".sh": "bash", ".fish": "bash", ".md": "markdown", ".ipynb": "json",
+    ".cfg": "ini", ".ini": "ini", ".csv": "", ".log": "", ".scad": "",
+}
+
+# Above this, re-parsing the whole file into a highlighted markdown block on
+# every render gets slow — large logs stay readable (unhighlighted) instead.
+HighlightCharLimit = 500_000
+
+
+def LanguageFor(EntryPath: Path) -> str:
+    return LanguageByExtension.get(EntryPath.suffix.lower(), "")
+
+
+def FencedBlock(Content: str, Language: str) -> str:
+    """A fence long enough that no run of backticks already in Content can
+    prematurely close it (CommonMark: closing fence >= opening fence length)."""
+    LongestRun = max((len(Run) for Run in re.findall(r"`+", Content)), default=0)
+    Fence = "`" * max(LongestRun + 1, 3)
+    return f"{Fence}{Language}\n{Content}\n{Fence}"
+
+
+class EditorView(ft.Container):
+    def __init__(
+        self,
+        EntryPath: Path,
+        FontFamily: str,
+        OnClose: Callable[[], None],
+        OnNotify: Callable[[str, str], None],
+    ):
+        self.EntryPath = EntryPath
+        self.OnClose = OnClose
+        self.OnNotify = OnNotify
+        self.Language = LanguageFor(EntryPath)
+
+        try:
+            self.OriginalContent = EntryPath.read_text(errors="replace")
+            self.ReadError: Optional[str] = None
+        except OSError as Error:
+            self.OriginalContent = ""
+            self.ReadError = str(Error)
+
+        self.IsEditing = False
+        self.IsDirty = False
+        self.SkipHighlight = len(self.OriginalContent) > HighlightCharLimit
+        CodeFont = ft.TextStyle(font_family=FontFamily, size=13)
+
+        self.TextField = ft.TextField(
+            value=self.OriginalContent,
+            multiline=True,
+            expand=True,
+            border=ft.InputBorder.NONE,
+            text_style=CodeFont,
+            on_change=self._OnTextChanged,
+        )
+        self.MarkdownView = ft.Markdown(
+            value=FencedBlock(self.OriginalContent, self.Language),
+            selectable=True,
+            extension_set=ft.MarkdownExtensionSet.GITHUB_FLAVORED,
+            code_theme=ft.MarkdownCodeTheme.ATOM_ONE_DARK,
+        )
+        self.PlainView = ft.Text(self.OriginalContent, selectable=True, style=CodeFont)
+
+        self.SaveButton = ft.OutlinedButton(
+            content="Save", style=ChipButtonStyle(), on_click=self._Save, disabled=True
+        )
+        self.ToggleButton = ft.OutlinedButton(content="Edit", style=ChipButtonStyle(), on_click=self._ToggleEdit)
+        self.StatusText = ft.Text("", color=Palette.Overlay0, size=12)
+
+        Toolbar = ft.Row(
+            [
+                ft.IconButton(
+                    icon=ft.Icons.ARROW_BACK, tooltip="Back to file list", on_click=lambda e: self.OnClose()
+                ),
+                ft.Text(EntryPath.name, weight=ft.FontWeight.BOLD, expand=True),
+                self.StatusText,
+                self.ToggleButton,
+                self.SaveButton,
+            ],
+            spacing=8,
+        )
+
+        if self.ReadError:
+            BodyContent: ft.Control = ft.Text(f"Couldn't read this file: {self.ReadError}", color=Palette.Red)
+        elif self.SkipHighlight:
+            BodyContent = self.PlainView
+        else:
+            BodyContent = self.MarkdownView
+        self.Body = ft.Container(content=BodyContent, expand=True, padding=12)
+
+        super().__init__(
+            content=ft.Column(
+                [Toolbar, ft.Divider(height=1, color=Palette.Surface1), self.Body], expand=True, spacing=8
+            ),
+            expand=True,
+            bgcolor=Palette.Base,
+            padding=12,
+        )
+
+    def _OnTextChanged(self, Event: ft.ControlEvent) -> None:
+        if not self.IsDirty:
+            self.IsDirty = True
+            self.SaveButton.disabled = False
+            self.StatusText.value = "Unsaved changes"
+            self.SaveButton.update()
+            self.StatusText.update()
+
+    def _ToggleEdit(self, Event: ft.ControlEvent) -> None:
+        if self.ReadError:
+            return
+        self.IsEditing = not self.IsEditing
+        if self.IsEditing:
+            self.Body.content = self.TextField
+            self.ToggleButton.content = "View"
+        else:
+            # Re-render the highlighted view from whatever's currently typed
+            # (even if unsaved), so Edit -> View -> Edit doesn't discard it.
+            if not self.SkipHighlight:
+                self.MarkdownView.value = FencedBlock(self.TextField.value, self.Language)
+            else:
+                self.PlainView.value = self.TextField.value
+            self.Body.content = self.PlainView if self.SkipHighlight else self.MarkdownView
+            self.ToggleButton.content = "Edit"
+        self.Body.update()
+        self.ToggleButton.update()
+
+    def _Save(self, Event: ft.ControlEvent) -> None:
+        try:
+            self.EntryPath.write_text(self.TextField.value)
+        except OSError as Error:
+            self.OnNotify(f"Couldn't save {self.EntryPath.name}: {Error}", "error")
+            return
+        self.OriginalContent = self.TextField.value
+        self.IsDirty = False
+        self.SaveButton.disabled = True
+        self.StatusText.value = "Saved."
+        self.SaveButton.update()
+        self.StatusText.update()
+        self.OnNotify(f"Saved {self.EntryPath.name}.", "success")