Buttons

Panels as classes

Each panel is a class:

• It holds the panel's values.
• Its Draw function builds the panel's controls.
• Controls are members of tachyon::GUIApplication, so Draw takes the app.

In my_app.h, after #include <gui_controls/gui_application.h>, #include <gui_controls/gui_dock_node.h> and #include <string>:

namespace my_app
{

// A count, and buttons that change it.
class CounterPanel
{
public:
    void Draw(tachyon::GUIApplication& ui);
 
    int count = 0;
};
 
// A few fields, and a greeting made from them.
class GreetingPanel
{
public:
    void Draw(tachyon::GUIApplication& ui);
 
    std::string name    = "World";
    int         times   = 1;
    bool        excited = false;
};

The counter panel

In my_app.cpp:

#include "my_app.h"
 
namespace my_app
{
    void CounterPanel::Draw(tachyon::GUIApplication& ui)
    {

ui.Text("Count: " + std::to_string(count));
 
ui.BeginHorizontal();
ui.Button("Add one", [this] { ++count; });
ui.Button("Reset",   [this] { count = 0; });
ui.EndHorizontal();

Close Draw with }.

• Draw runs every frame and describes the panel as it is now, so the text always shows the current count.
• No IDs are needed:
  • The library keeps a control's state between frames under its ID.
  • Each control here takes its ID from its call site, the file and line of the call.
  • The call site stays the same across frames, so the ID does too.
• BeginHorizontal/EndHorizontal put the buttons in a row.
  • Every Begin* needs its End*, whether or not the Begin* returned true.
• A button's callback runs after all controls are built.
  • So it can change the panel's values freely.
  • The next frame shows the result.
• [this] is safe because the app owns the panel (step 4).

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