UI: Button: initial =>

 * Control: design complete;
 * Window: handles controls on it;
 * Idle: no more 100% CPU load for no reason

os/ui/gl/sdl/h3r_sdlwindow.cpp

@@ -167,10 +167,13 @@ void SDLWindow::ProcessMessages()
         switch (_e.type) {
             case SDL_WINDOWEVENT: HandleWindowEvent (); break;
             case SDL_KEYUP: HandleKeyboardEvent (e); break;
+            case SDL_MOUSEMOTION: HandleMouseMotionEvent (e); break;
         }
     }
 }// ProcessMessages
 
+bool SDLWindow::Idle() { return ! SDL_PollEvent (nullptr); }
+
 void SDLWindow::HandleWindowEvent()
 {
     THE_WAY_IS_SHUT
@@ -199,4 +202,17 @@ void SDLWindow::HandleKeyboardEvent(EventArgs & e)
     }
 }
 
+void SDLWindow::HandleMouseMotionEvent(EventArgs & e)
+{
+    THE_WAY_IS_SHUT
+
+    //TODO _e.motion.which; the mouse instance id
+    //     Please don't play with more than one mouse simultaneously :)
+
+    e.X = _e.motion.x;
+    e.Y = _e.motion.y;
+    OnMouseMove (e);
+    e.X = e.Y = 0;
+}
+
 NAMESPACE_H3R

os/ui/gl/sdl/h3r_sdlwindow.h

@@ -62,10 +62,12 @@ class SDLWindow : public OSWindow
     protected virtual void Show() override;
     protected inline virtual void Hide() override { _visible = false; }
     protected inline virtual void Close() override { _q = true; }
-    private void Render();
+    protected void Render() override;
+    protected bool Idle() override;
     private void Resized();
     private void HandleWindowEvent();
     private void HandleKeyboardEvent(EventArgs &);
+    private void HandleMouseMotionEvent(EventArgs &);
     public void ProcessMessages() override;
     public SDLWindow(int, char **);
     public ~SDLWindow();

os/ui/h3r_oswindow.h

@@ -51,6 +51,8 @@ class OSWindow : public IWindow
     public virtual void Hide () override {}
     public virtual void Close () override {}
     public virtual void ProcessMessages() override {}
+    public virtual bool Idle() override { return true; }
+    public virtual void Render() override {}
 
     public OSWindow(int, char **) {}
     public virtual ~OSWindow() {}

ui/h3r_box.h

@@ -41,9 +41,15 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 H3R_NAMESPACE
 
 // Base for all 2D rectangular areas. I like the short name.
-class Box
+class Box final
 {
-    public: virtual bool Contains(Point &) { return false; }
+    public: inline bool Contains(Point & p)
+    {
+        return p.X >= Pos.X && p.X < (Pos.X + Size.X)
+            && p.Y >= Pos.Y && p.Y < (Pos.Y + Size.Y);
+    }
+    public: Point Pos;
+    public: Point Size;
 };
 
 NAMESPACE_H3R

ui/h3r_button.cpp

@@ -0,0 +1,72 @@
+/**** BEGIN LICENSE BLOCK ****
+
+BSD 3-Clause License
+
+Copyright (c) 2021-2023, the wind.
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+3. Neither the name of the copyright holder nor the names of its
+   contributors may be used to endorse or promote products derived from
+   this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+**** END LICENCE BLOCK ****/
+
+#include "h3r_button.h"
+// #include "h3r_log.h"
+// #include "h3r_string.h"
+
+H3R_NAMESPACE
+
+Button::Button(const String &, Control * base)
+    : Control {base}
+{
+    Resize (100, 20);
+    SetPos (500, 20);
+}
+
+void Button::OnMouseMove(const EventArgs & e)
+{
+    static Point p;
+    p.X = e.X;
+    p.Y = e.Y;
+    _mouse_over = HitTest (p);
+    /*Log::Info (String::Format (
+        "Button::OnMouseMove (%d, %d), hover: %d, _bb (%d, %d, %d, %d)" EOL,
+        p.X, p.Y, _mouse_over,
+        ClientRectangle ().Pos.X, ClientRectangle ().Pos.Y,
+        ClientRectangle ().Size.X, ClientRectangle ().Size.Y));*/
+}
+
+void Button::OnRender(GC & gc)
+{
+    glLoadIdentity ();
+    glDisable (GL_TEXTURE_2D); // implict contract with MainWindow.Show()
+                               //LATER to the render engine
+    if (! _mouse_over) glColor3d (1.0, 1.0, 1.0);
+    else glColor3d (0.0, 1.0, 0.0);
+    gc.RenderBox (ClientRectangle ());
+    glEnable (GL_TEXTURE_2D);
+}
+
+NAMESPACE_H3R

ui/h3r_mkstate.h → ui/h3r_button.h

@@ -32,16 +32,28 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 **** END LICENCE BLOCK ****/
 
-#ifndef _H3R_MKSTATE_H_
-#define _H3R_MKSTATE_H_
+#ifndef _H3R_BUTTON_H_
+#define _H3R_BUTTON_H_
 
 #include "h3r.h"
+#include "h3r_string.h"
+#include "h3r_point.h"
+#include "h3r_gc.h"
+#include "h3r_control.h"
+#include "h3r_eventargs.h"
 
 H3R_NAMESPACE
 
-// Mouse and Keyboard state.
-class MKState
+// Its size is stored at the resource it is created from.
+class Button: public Control
 {
+    public: Button(const String &, Control *);
+    public: virtual ~Button() override {}
+
+    public: virtual void OnRender(GC &) override;
+    public: virtual void OnMouseMove(const EventArgs &) override;
+
+    private: bool _mouse_over {};
 };
 
 NAMESPACE_H3R

ui/h3r_control.cpp

@@ -36,34 +36,34 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 H3R_NAMESPACE
 
-Control * Control::Active {};
-
-Control * Control::Root()
+void Control::Add(Control * c)
 {
-    static Control r;
-    return &r;
+    // Adding one and the same thing twice speaks for an error somewhere;
+    // Allowing it will slow things down. Ignoring it would leave wrong code.
+    H3R_ARG_EXC_IF(_z.Contains (c), "duplicate pointer: fix your code")
+    H3R_ARG_EXC_IF(nullptr == c, "c can't be null")
+    _z.Add (c);
 }
 
-void Control::Add(Control * c) //TODO else
-{
-    if (! _z.Contains (c))
-        _z.Add (c);
-}
+Control::Control(Control * base) { if (base) base->Add (this); }
 
-Control::Control(Control * base)
+void Control::Resize(int w, int h)
 {
-    if (! base) base = Control::Root ();
-    base->Add (this);
+    _bb.Size.X = w;
+    _bb.Size.Y = h;
 }
-
-bool Control::HitTest(Point & p)
+void Control::SetPos(int x, int y)
 {
-    return _bb.Contains (p);
+    _bb.Pos.X = x;
+    _bb.Pos.Y = y;
 }
 
+bool Control::HitTest(Point & p) { return _bb.Contains (p); }
+
 void Control::OnEvent(Event & e)
 {
-    e.Do (this);
+    EventArgs foo;
+    e.Do (*this, foo);
 }
 
 NAMESPACE_H3R

ui/h3r_control.h

@@ -46,7 +46,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include "h3r_point.h"
 #include "h3r_box.h"
 #include "h3r_gc.h"
-#include "h3r_mkstate.h"
+#include "h3r_eventargs.h"
 #include "h3r_event.h"
 
 H3R_NAMESPACE
@@ -55,31 +55,45 @@ H3R_NAMESPACE
 // Coordinate system:
 //  right: +x; left: -x; top: -y; bottom: +y; 0,0 as top left screen corner;
 //  w,h [pixels]
-
+//
+// Absolute coordinates, because there is no auto-layout being done, and because
+// this isn't a generic UI framework. The local CS, should it becomes a
+// necessity, is -Pos();
 class Control
 {
+    private: Box _bb; // bounding box
+
     private: List<Control *> _z;   // z-order; render: from 0 to count-1
-    private: List<Control *> _n;   // non-visible ones
+    private: List<Control *> _n;   //LATER non-visible ones; if any
     private: void Add(Control *);
-    private: static Control * Active;     // receives input
-    private: Control() {}
-    private: static Control * Root();     // refers all controls
-    public: Control(Control *);
 
-    private: Box _bb; // bounding box
-    protected: virtual bool HitTest(Point & p); // [input function]
+    public: Control(Control * = nullptr);
+    public: virtual ~Control() {}
+
+    public: const Point & Pos() { return _bb.Pos; }
+    public: const Point & Size() { return _bb.Size; }
+    public: void SetPos(int, int);
 
-    private: bool _visible;
-    public: static void NotifyDraw(GC &); // Entry point for Draw
-    protected: void DoDraw(GC &);         // TreeWalk(OnDraw)
+    protected: inline Box & ClientRectangle() { return _bb; }
+    protected: void Resize(int, int);
+    protected: virtual bool HitTest(Point & p);
 
-    // do not check _visible here; there is visible list and a non-visible one -
+    // Do not check _visible here; there is visible list and a non-visible one -
     // controlled by event-driven logic; no need to check visibility each time
-    // draw is issued
-    protected: virtual void Draw(GC &) {}
-    protected: virtual void MouseEvent(MKState &) {}
-    protected: virtual void KeyboardEvent(MKState &) {}
-    protected: virtual void OnEvent(Event &); // when the above 2 are not enough
+    // render is issued.
+    // No UI editor so these remain empty.
+    //TODO figure out a way for the subject(window) to notify its observers
+    //     w/o publishing these methods for everyone to call
+    public: virtual void OnRender(GC &) {}
+    public: virtual void OnMouseMove(const EventArgs &) {}
+    public: virtual void OnMouseUp(const EventArgs &) {}
+    public: virtual void OnMouseDown(const EventArgs &) {}
+    public: virtual void OnKeyDown(const EventArgs &) {}
+    public: virtual void OnKeyUp(const EventArgs &) {}
+
+    //TODO hint system; MyHint: Event ... show_hint (myhint);
+    //     Control.RMB += (Event & ShowHint) => Root().OnEvent (ShowHint);
+    public: virtual void OnEvent(Event &);
 };
 
 NAMESPACE_H3R

ui/h3r_event.h

@@ -66,12 +66,17 @@ class Event
     // public: void Attach(Event *); // aka foo.Changed += bar
     // public: void Detach(Event *); // aka foo.Changed -= bar
     private Event * _next;
-    public Event(Event * next_eh = nullptr) : _next{next_eh} {}
-    public virtual void Do(class Control * c) { if (_next) _next->Do (c); }
+    public Event(Event * next_eh = nullptr)
+        : _next{next_eh} {}
+    public inline virtual void Do(
+        class Control & sender, struct EventArgs & args)
+    {
+        if (_next) _next->Do (sender, args);
+    }
     // Implement this when your object has "doubts" about handling something
-    public virtual bool Handled() { return true; }
+    public inline virtual bool Handled() { return true; }
     // Why is this "virtual" eludes me still. Perhaps on the next re-read.
-    public virtual void SetNext(Event * next_eh) { _next = next_eh; }
+    public inline virtual void SetNext(Event * next_eh) { _next = next_eh; }
 };
 
 // The book responsible for code like the above one:

ui/h3r_gc.h

@@ -36,13 +36,35 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #define _H3R_GC_H_
 
 #include "h3r.h"
+#include "h3r_box.h"
+#include "GL/gl.h"
 
 H3R_NAMESPACE
 
-// Graphics Context
+// Graphics Context.
+// A collection of rendering functions. Simplifies all other rendering code.
+// This is where the glyph and sprite cache will be.
+// You can always replace these with shaders, or whatever.
+//
+// The game rendering includes:
+//   * Sprite (animated; with an FPS, group parameter)
+//   * Text (1 sprite per glyph, rendered as the font engine says so)
+//   * Line (the cursor for the text edit box (which is text rendering again))
+//   * Video
+// There is no color state here. Everything is pre-encoded at the game data.
 class GC
 {
     public: static GC * Current;
+
+    public: inline void RenderBox(const Box & b)
+    {
+        glBegin (GL_LINE_LOOP);
+            glVertex2d (b.Pos.X         , b.Pos.Y         );
+            glVertex2d (b.Pos.X         , b.Pos.Y+b.Size.Y);
+            glVertex2d (b.Pos.X+b.Size.X, b.Pos.Y+b.Size.Y);
+            glVertex2d (b.Pos.X+b.Size.X, b.Pos.Y         );
+        glEnd ();
+    }
 };
 
 NAMESPACE_H3R

ui/h3r_iwindow.h

@@ -59,6 +59,12 @@ struct IWindow
     // The thing to periodically do while waiting for an async task to complete.
     virtual void ProcessMessages() {H3R_NOT_IMPLEMENTED_EXC}
 
+    // Return true to indicate there are no messages to process.
+    virtual bool Idle() {H3R_NOT_IMPLEMENTED_EXC}
+
+    // A.k.a. Update(); a.k.a. Refresh(); etc.
+    virtual void Render() {H3R_NOT_IMPLEMENTED_EXC}
+
     virtual ~IWindow() {}
 
     // Events