Cache the preferred size of widgets

NanoGUI potentially spends a significant amount of runtime in the
functions ``nvgTextBounds()`` and ``nvgTextBoxBounds()`` that are used
to compute the preferred size of widgets.

This commit adopts a strategy that caches the preferred size in
bottom-level widgets (i.e., ones that don't layout a set of child
widgets).

The main complication is that various kinds of changes (setting
different captions, themes, etc.) can invalidate the precomputed
preferred size, so a relatively large number of setters need touchups.

Author: wjakob

include/nanogui/button.h

@@ -59,7 +59,12 @@ class NANOGUI_EXPORT Button : public Widget {
     std::string_view caption() const { return m_caption; }
 
     /// Sets the caption of this Button.
-    void set_caption(std::string_view caption) { m_caption = caption; }
+    void set_caption(std::string_view caption) {
+        if (m_caption != caption) {
+            m_caption = caption;
+            preferred_size_changed();
+        }
+    }
 
     /// Returns the background color of this Button.
     const Color &background_color() const { return m_background_color; }
@@ -74,7 +79,12 @@ class NANOGUI_EXPORT Button : public Widget {
     /// Returns the icon of this Button.  See \ref nanogui::Button::m_icon.
     int icon() const { return m_icon; }
     /// Sets the icon of this Button.  See \ref nanogui::Button::m_icon.
-    void set_icon(int icon) { m_icon = icon; }
+    void set_icon(int icon) {
+        if (m_icon != icon) {
+            m_icon = icon;
+            preferred_size_changed();
+        }
+    }
 
     /// The current flags of this Button (see \ref nanogui::Button::Flags for options).
     int flags() const { return m_flags; }
@@ -84,7 +94,12 @@ class NANOGUI_EXPORT Button : public Widget {
     /// The position of the icon for this Button.
     IconPosition icon_position() const { return m_icon_position; }
     /// Sets the position of the icon for this Button.
-    void set_icon_position(IconPosition icon_position) { m_icon_position = icon_position; }
+    void set_icon_position(IconPosition icon_position) {
+        if (m_icon_position != icon_position) {
+            m_icon_position = icon_position;
+            preferred_size_changed();
+        }
+    }
 
     /// Whether or not this Button is currently pushed.
     bool pushed() const { return m_pushed; }
@@ -109,10 +124,18 @@ class NANOGUI_EXPORT Button : public Widget {
     /// The padding of this Button.
     const Vector2i &padding() const { return m_padding; }
     /// Set the padding of this Button.
-    void set_padding(const Vector2i &padding) { m_padding = padding; }
+    void set_padding(const Vector2i &padding) {
+        if (m_padding != padding) {
+            m_padding = padding;
+            preferred_size_changed();
+        }
+    }
 
+protected:
     /// The preferred size of this Button.
-    virtual Vector2i preferred_size(NVGcontext *ctx) const override;
+    virtual Vector2i preferred_size_impl(NVGcontext *ctx) const override;
+
+public:
     /// The callback that is called when any type of mouse button event is issued to this Button.
     virtual bool mouse_enter_event(const Vector2i &p, bool enter) override;
     virtual bool mouse_button_event(const Vector2i &p, int button, bool down, int modifiers) override;

include/nanogui/checkbox.h

@@ -52,7 +52,12 @@ class NANOGUI_EXPORT CheckBox : public Widget {
     std::string_view caption() const { return m_caption; }
 
     /// Sets the caption of this check box
-    void set_caption(std::string_view caption) { m_caption = caption; }
+    void set_caption(std::string_view caption) {
+        if (m_caption != caption) {
+            m_caption = caption;
+            preferred_size_changed();
+        }
+    }
 
     /// Return whether or not this widget is currently checked.
     const bool &checked() const { return m_checked; }
@@ -73,8 +78,11 @@ class NANOGUI_EXPORT CheckBox : public Widget {
     /// Mouse button event processing for this check box
     virtual bool mouse_button_event(const Vector2i &p, int button, bool down, int modifiers) override;
 
+protected:
     /// The preferred size of this CheckBox.
-    virtual Vector2i preferred_size(NVGcontext *ctx) const override;
+    virtual Vector2i preferred_size_impl(NVGcontext *ctx) const override;
+
+public:
 
     /// Draws this CheckBox.
     virtual void draw(NVGcontext *ctx) override;

include/nanogui/colorwheel.h

@@ -50,8 +50,6 @@ class NANOGUI_EXPORT ColorWheel : public Widget {
     /// Sets the current Color this ColorWheel has selected.
     void set_color(const Color& color);
 
-    /// The preferred size of this ColorWheel.
-    virtual Vector2i preferred_size(NVGcontext *ctx) const override;
 
     /// Draws the ColorWheel.
     virtual void draw(NVGcontext *ctx) override;
@@ -99,6 +97,9 @@ class NANOGUI_EXPORT ColorWheel : public Widget {
 
     /// The current callback to execute when the color value has changed.
     std::function<void(const Color &)> m_callback;
+
+    /// The preferred size of this ColorWheel.
+    virtual Vector2i preferred_size_impl(NVGcontext *ctx) const override;
 };
 
 NAMESPACE_END(nanogui)

include/nanogui/graph.h

@@ -50,9 +50,9 @@ class NANOGUI_EXPORT Graph : public Widget {
     std::vector<float> &values() { return m_values; }
     void set_values(const std::vector<float> &values) { m_values = values; }
 
-    virtual Vector2i preferred_size(NVGcontext *ctx) const override;
     virtual void draw(NVGcontext *ctx) override;
 protected:
+    virtual Vector2i preferred_size_impl(NVGcontext *ctx) const override;
     std::string m_caption, m_header, m_footer;
     Color m_background_color, m_fill_color, m_stroke_color, m_text_color;
     std::vector<float> m_values;

include/nanogui/imagepanel.h

@@ -28,7 +28,7 @@ class NANOGUI_EXPORT ImagePanel : public Widget {
 public:
     ImagePanel(Widget *parent);
 
-    void set_images(const Images &data) { m_images = data; }
+    void set_images(const Images &data) { m_images = data; preferred_size_changed(); }
     const Images& images() const { return m_images; }
 
     const std::function<void(int)> &callback() const { return m_callback; }
@@ -38,10 +38,10 @@ class NANOGUI_EXPORT ImagePanel : public Widget {
                                     int modifiers) override;
     virtual bool mouse_button_event(const Vector2i &p, int button, bool down,
                                     int modifiers) override;
-    virtual Vector2i preferred_size(NVGcontext *ctx) const override;
     virtual void draw(NVGcontext *ctx) override;
 
 protected:
+    virtual Vector2i preferred_size_impl(NVGcontext *ctx) const override;
     Vector2i grid_size() const;
     int index_for_position(const Vector2i &p) const;
 protected:

include/nanogui/label.h

@@ -32,10 +32,20 @@ class NANOGUI_EXPORT Label : public Widget {
     /// Get the label's text caption
     std::string_view caption() const { return m_caption; }
     /// Set the label's text caption
-    void set_caption(std::string_view caption) { m_caption = caption; }
+    void set_caption(std::string_view caption) {
+        if (m_caption != caption) {
+            m_caption = caption;
+            preferred_size_changed();
+        }
+    }
 
     /// Set the currently active font (2 are available by default: 'sans' and 'sans-bold')
-    void set_font(std::string_view font) { m_font = font; }
+    void set_font(std::string_view font) {
+        if (m_font != font) {
+            m_font = font;
+            preferred_size_changed();
+        }
+    }
     /// Get the currently active font
     std::string_view font() const { return m_font; }
 
@@ -47,8 +57,11 @@ class NANOGUI_EXPORT Label : public Widget {
     /// Set the \ref Theme used to draw this widget
     virtual void set_theme(Theme *theme) override;
 
+protected:
     /// Compute the size needed to fully display the label
-    virtual Vector2i preferred_size(NVGcontext *ctx) const override;
+    virtual Vector2i preferred_size_impl(NVGcontext *ctx) const override;
+
+public:
 
     /// Draw the label
     virtual void draw(NVGcontext *ctx) override;

include/nanogui/progressbar.h

@@ -28,9 +28,9 @@ class NANOGUI_EXPORT ProgressBar : public Widget {
     float value() { return m_value; }
     void set_value(float value) { m_value = value; }
 
-    virtual Vector2i preferred_size(NVGcontext *ctx) const override;
     virtual void draw(NVGcontext* ctx) override;
 protected:
+    virtual Vector2i preferred_size_impl(NVGcontext *ctx) const override;
     float m_value;
 };
 

include/nanogui/python.h

@@ -61,8 +61,8 @@ extern "C" {
     bool keyboard_character_event(unsigned int codepoint) override {           \
         NB_OVERRIDE(keyboard_character_event, codepoint);                      \
     }                                                                          \
-    ::nanogui::Vector2i preferred_size(NVGcontext *ctx) const override {       \
-        NB_OVERRIDE(preferred_size, ctx);                                      \
+    ::nanogui::Vector2i preferred_size_impl(NVGcontext *ctx) const override {  \
+        NB_OVERRIDE(preferred_size_impl, ctx);                                 \
     }                                                                          \
     void perform_layout(NVGcontext *ctx) override {                            \
         NB_OVERRIDE(perform_layout, ctx);                                      \

include/nanogui/slider.h

@@ -43,7 +43,10 @@ class NANOGUI_EXPORT Slider : public Widget {
     const std::function<void(float)> &final_callback() const { return m_final_callback; }
     void set_final_callback(const std::function<void(float)> &callback) { m_final_callback = callback; }
 
-    virtual Vector2i preferred_size(NVGcontext *ctx) const override;
+protected:
+    virtual Vector2i preferred_size_impl(NVGcontext *ctx) const override;
+
+public:
     virtual bool mouse_drag_event(const Vector2i &p, const Vector2i &rel, int button, int modifiers) override;
     virtual bool mouse_button_event(const Vector2i &p, int button, bool down, int modifiers) override;
     virtual void draw(NVGcontext* ctx) override;

include/nanogui/tabwidget.h

@@ -60,19 +60,19 @@ class NANOGUI_EXPORT TabWidgetBase : public Widget {
     /// Return the caption of the tab with the given ID
     const std::string& tab_caption(int id) const { return m_tab_captions[tab_index(id)]; }
     /// Change the caption of the tab with the given ID
-    void set_tab_caption(int id, std::string_view caption) { m_tab_captions[tab_index(id)] = caption; }
+    void set_tab_caption(int id, std::string_view caption) { m_tab_captions[tab_index(id)] = caption; preferred_size_changed(); }
 
     /// Return whether tabs provide a close button
     bool tabs_closeable() const { return m_tabs_closeable; }
-    void set_tabs_closeable(bool value) { m_tabs_closeable = value; }
+    void set_tabs_closeable(bool value) { m_tabs_closeable = value; preferred_size_changed(); }
 
     /// Return whether tabs can be dragged to different positions
     bool tabs_draggable() const { return m_tabs_draggable; }
     void set_tabs_draggable(bool value) { m_tabs_draggable = value; }
 
     /// Return the padding between the tab widget boundary and child widgets
     int padding() const { return m_padding; }
-    void set_padding(int value) { m_padding = value; }
+    void set_padding(int value) { m_padding = value; preferred_size_changed(); }
 
     /// Set the widget's background color (a global property)
     void set_background_color(const Color &background_color) {
@@ -101,7 +101,6 @@ class NANOGUI_EXPORT TabWidgetBase : public Widget {
 
     // Widget implementation
     virtual void perform_layout(NVGcontext* ctx) override;
-    virtual Vector2i preferred_size(NVGcontext* ctx) const override;
     virtual void draw(NVGcontext* ctx) override;
     virtual bool mouse_button_event(const Vector2i &p, int button, bool down,
                                     int modifiers) override;
@@ -110,6 +109,7 @@ class NANOGUI_EXPORT TabWidgetBase : public Widget {
                                     int modifiers) override;
 
 protected:
+    virtual Vector2i preferred_size_impl(NVGcontext* ctx) const override;
     std::pair<int, bool> tab_at_position(const Vector2i &p,
                                          bool test_vertical = true) const;
     virtual void update_visibility();
@@ -198,8 +198,8 @@ class NANOGUI_EXPORT TabWidget : public TabWidgetBase {
     void set_remove_children(bool value) { m_remove_children = value; }
 
     virtual void perform_layout(NVGcontext* ctx) override;
-    virtual Vector2i preferred_size(NVGcontext* ctx) const override;
 protected:
+    virtual Vector2i preferred_size_impl(NVGcontext* ctx) const override;
     virtual void update_visibility() override;
 protected:
     std::vector<std::pair<int, Widget *>> m_widgets;