visibility and size constraint

src/dlangui/widgets/styles.d

@@ -13,6 +13,8 @@ immutable ushort FONT_WEIGHT_UNSPECIFIED = 0x0000;
 immutable ubyte FONT_STYLE_UNSPECIFIED = 0xFF;
 immutable ubyte FONT_STYLE_NORMAL = 0x00;
 immutable ubyte FONT_STYLE_ITALIC = 0x01;
+/// use as widget.layout() param to avoid applying of parent size
+immutable int SIZE_UNSPECIFIED = int.max;
 
 enum Align : ubyte {
     Unspecified = ALIGN_UNSPECIFIED,
@@ -45,6 +47,10 @@ class Style {
 	protected string _backgroundImageId;
 	protected Rect _padding;
 	protected Rect _margins;
+    protected int _minWidth = SIZE_UNSPECIFIED;
+    protected int _maxWidth = SIZE_UNSPECIFIED;
+    protected int _minHeight = SIZE_UNSPECIFIED;
+    protected int _maxHeight = SIZE_UNSPECIFIED;
 
 	protected Style[] _substates;
 	protected Style[] _children;
@@ -194,6 +200,59 @@ class Style {
             return parentStyle.backgroundImageId;
 	}
 
+    //===================================================
+    // size restrictions
+
+	/// minimal width constraint, 0 if limit is not set
+	@property uint minWidth() const {
+        if (_minWidth != SIZE_UNSPECIFIED)
+            return _minWidth;
+        else
+            return parentStyle.minWidth;
+	}
+	/// max width constraint, returns SIZE_UNSPECIFIED if limit is not set
+	@property uint maxWidth() const {
+        if (_maxWidth != SIZE_UNSPECIFIED)
+            return _maxWidth;
+        else
+            return parentStyle.maxWidth;
+	}
+	/// minimal height constraint, 0 if limit is not set
+	@property uint minHeight() const {
+        if (_minHeight != SIZE_UNSPECIFIED)
+            return _minHeight;
+        else
+            return parentStyle.minHeight;
+	}
+	/// max height constraint, SIZE_UNSPECIFIED if limit is not set
+	@property uint maxHeight() const {
+        if (_maxHeight != SIZE_UNSPECIFIED)
+            return _maxHeight;
+        else
+            return parentStyle.maxHeight;
+	}
+    /// set min width constraint
+    @property Style minWidth(int value) {
+        _minWidth = value;
+        return this;
+    }
+    /// set max width constraint
+    @property Style maxWidth(int value) {
+        _maxWidth = value;
+        return this;
+    }
+    /// set min height constraint
+    @property Style minHeight(int value) {
+        _minHeight = value;
+        return this;
+    }
+    /// set max height constraint
+    @property Style maxHeight(int value) {
+        _maxHeight = value;
+        return this;
+    }
+
+
     //===================================================
     // alignment
 
@@ -326,6 +385,8 @@ class Theme : Style {
 		_fontWeight = 400;
 		_fontFace = "Arial"; // TODO: from settings
         _fontFamily = FontFamily.SansSerif;
+        _minHeight = 0;
+        _minWidth = 0;
 	}
 
 	/// create wrapper style which will have currentTheme.get(id) as parent instead of fixed parent - to modify some base style properties in widget

src/dlangui/widgets/widget.d

@@ -5,11 +5,29 @@ public import dlangui.widgets.styles;
 public import dlangui.graphics.drawbuf;
 public import dlangui.graphics.images;
 public import dlangui.graphics.fonts;
+
 import dlangui.platforms.common.platform;
 
+import std.algorithm;
+
+
+/// Visibility (see Android View Visibility)
+enum Visibility : ubyte {
+    /// Visible on screen (default)
+    Visible,
+    /// Not visible, but occupies a space in layout
+    Invisible,
+    /// Completely hidden, as not has been added
+    Gone
+}
+
 class Widget {
+    /// widget id
+    protected string _id;
     /// current widget position, set by layout()
     protected Rect _pos;
+    /// widget visibility: either Visible, Invisible, Gone
+    protected Visibility _visibility = Visibility.Visible; // visible by default
     /// style id to lookup style in theme
 	protected string _styleId;
     /// own copy of style - to override some of style properties, null of no properties overriden
@@ -45,13 +63,20 @@ class Widget {
 		return _ownStyle;
 	}
 
+    /// returns widget id, null if not set
+	@property string id() const { return _styleId; }
+    /// set widget id
+    @property void id(string id) { _id = id; }
+    /// compare widget id with specified value, returs true if matches
+    bool compareId(string id) { return (_id !is null) && id.equal(_id); }
+
     //======================================================
     // Style related properties
 
     /// returns widget style id, null if not set
-    @property void styleId(string id) { _styleId = id; }
-    /// set widget style id
 	@property string styleId() const { return _styleId; }
+    /// set widget style id
+    @property void styleId(string id) { _styleId = id; }
     /// get margins (between widget bounds and its background)
     @property Rect margins() const { return style.margins; }
     /// set margins for widget - override one from style
@@ -119,12 +144,54 @@ class Widget {
     @property int width() { return _pos.width; }
     /// returns current height of widget in pixels
     @property int height() { return _pos.height; }
-    /// Measure widget according to desired width and height constraints. (Step 1 of two phase layout).
+
-    void measure(int width, int height) { 
+    /// returns widget visibility (Visible, Invisible, Gone)
-        _measuredWidth = _measuredHeight = 0;
+    @property Visibility visibility() { return _visibility; }
+    /// sets widget visibility (Visible, Invisible, Gone)
+    @property Widget visibility(Visibility visible) { 
+        _visibility = visible; 
+        requestLayout();
+        return this;
     }
+
+    /// request relayout of widget and its children
+    void requestLayout() {
+        _needLayout = true;
+    }
+    /// request redraw
+    void invalidate() {
+        _needDraw = true;
+    }
+
+    /// Measure widget according to desired width and height constraints. (Step 1 of two phase layout).
+    void measure(int parentWidth, int parentHeight) { 
+        measuredContent(parentWidth, parentHeight, 0, 0);
+    }
+
+    /// helper function for implement measure() when widget's content dimensions are known
+    protected void measuredContent(int parentWidth, int parentHeight, int contentWidth, int contentHeight) {
+        if (visibility == Visibility.Gone) {
+            _measuredWidth = _measuredHeight = 0;
+            return;
+        }
+        Rect m = margins;
+        Rect p = padding;
+        int dx = m.left + m.right + p.left + p.right + contentWidth;
+        int dy = m.top + m.bottom + p.top + p.bottom + contentHeight;
+        // check for margins and padding
+        if (parentWidth != SIZE_UNSPECIFIED && dx > parentWidth)
+            dx = parentWidth;
+        if (parentHeight != SIZE_UNSPECIFIED && dy > parentHeight)
+            dy = parentHeight;
+        _measuredWidth = dx;
+        _measuredHeight = dy;
+    }
+
     /// Set widget rectangle to specified value and layout widget contents. (Step 2 of two phase layout).
     void layout(Rect rc) {
+        if (visibility == Visibility.Gone) {
+            return;
+        }
         _pos = rc;
         _needLayout = false;
     }
@@ -146,6 +213,8 @@ class Widget {
     }
     /// Draw widget at its position to buffer
     void onDraw(DrawBuf buf) {
+        if (visibility != Visibility.Visible)
+            return;
         Rect rc = _pos;
         applyMargins(rc);
         buf.fillRect(_pos, backgroundColor);
@@ -198,6 +267,19 @@ class Widget {
     @property int childCount() { return 0; }
     /// returns child by index
     Widget child(int index) { return null; }
+    /// find child by id, returns null if not found
+    Widget childById(string id) { 
+        if (compareId(id))
+            return this;
+        // lookup children
+        for (int i = childCount - 1; i >= 0; i--) {
+            Widget res = child(i).childById(id);
+            if (res !is null)
+                return res;
+        }
+        // not found
+        return null; 
+    }
     /// returns parent widget, null for top level widget
     @property Widget parent() { return _parent; }
     /// sets parent for widget