Native Input Hosts

Most ModernUI controls are painted on a CCanvas-backed surface.

Text editing is different.

For real text editing, ModernUI uses native MT5 chart objects such as OBJ_EDIT behind host controls.

This gives users normal text editing behaviour, but it also creates extra lifecycle and positioning rules.

Host controls

Native host behaviour is relevant to controls such as:

MuiTextBoxHost
MuiTextAreaHost
MuiSpinEditHost
MuiComboBoxHost

Some of these combine canvas-painted UI with native edit/input chrome.

Why hosts exist

Canvas-only text input is limited.

Native hosts help with:

typing
editing
caret behaviour
selection
copy/paste
native keyboard input

Sync behaviour

Native hosts sync from the root during paint/layout paths.

Important sync concerns:

chart position
control geometry
clipping
visibility
focus
chart object size
chart object visibility

The host should not be moved or recreated on every mouse move.

Cleanup

Always call g_ui.Shutdown() in OnDeinit().

void OnDeinit(const int reason)
{
  g_ui.Shutdown();
}

This lets hosts remove their native chart objects cleanly.

TextBox example

MuiTextBoxHost *name=Mui::TextBox(parent,"Default name",260.0,0.0);

For form layouts:

MuiLabeledTextBox profile=Mui::LabeledTextBox(
  section.body,
  "Profile name",
  "Default",
  0.0,
  0.0,
  "Native text editing."
);

TextArea example

MuiTextAreaHost *notes=Mui::TextArea(parent,"",420.0,0.0,false);

For form layouts:

MuiLabeledTextArea notes=Mui::LabeledTextArea(
  section.body,
  "Notes",
  "",
  0.0,
  0.0,
  "Optional."
);

MT5 limitations

Native chart objects are not the same as normal desktop UI controls.

Expect constraints around:

clipping
z-order
chart redraw timing
exact positioning during scroll/resize
styling limitations
behaviour differences across terminal builds

ModernUI hides as much of this as practical, but it cannot make MT5 behave exactly like a native desktop UI toolkit.

Common mistakes

Forgetting shutdown

If native chart objects remain after removing an EA, check g_ui.Shutdown().

Recreating native inputs unnecessarily

Update existing controls when possible.

Expecting full CSS-like styling

Native host objects have MT5 limitations. Use ModernUI theming and setters where supported.

Putting too many text inputs in tiny panels

Native input hosts are heavier than labels/buttons. Keep compact panels focused.