Automate "linux/my_application.cc" modification

[larsb24]

Hey,

I was thinking about automating the required modification in linux/my_application.cc for easier use.
Do you think having the change (switching the lines) can do any potential harm to an application that don't use handy_window?
Because otherwise the easiest way to do that is probably just changing the default my_application.cc

[jpnurmi]

Technically, it should be enough to move gtk_widget_show(window) after fl_register_plugins() and this is the change I originally planned to propose to the Flutter app template:

diff --git a/linux/my_application.cc b/linux/my_application.cc
index 6f18193..6900d28 100644
--- a/linux/my_application.cc
+++ b/linux/my_application.cc
@@ -48,7 +48,6 @@ static void my_application_activate(GApplication* application) {
   }
 
   gtk_window_set_default_size(window, 1280, 720);
-  gtk_widget_show(GTK_WIDGET(window));
 
   g_autoptr(FlDartProject) project = fl_dart_project_new();
   fl_dart_project_set_dart_entrypoint_arguments(project, self->dart_entrypoint_arguments);
@@ -59,6 +58,7 @@ static void my_application_activate(GApplication* application) {
 
   fl_register_plugins(FL_PLUGIN_REGISTRY(view));
 
+  gtk_widget_show(GTK_WIDGET(window));
   gtk_widget_grab_focus(GTK_WIDGET(view));
 }
 

However, the FlView implementation assumes that GtkWidget::size-allocate and GtkWidget::realize get called in a specific order. While the above patch works by coincidence with handy_window, a vanilla Flutter/GTK window stays empty on startup until e.g. resized.

As a workaround, moving gtk_widget_show(view) after gtk_widget_show(window) helps to restore the desired order for size-allocate and realize. This is also what's currently proposed in the README file to make sure that the vanilla Flutter/GTK window doesn't show up empty if a Handy window cannot be set up for one reason or another.

diff --git a/linux/my_application.cc b/linux/my_application.cc
index 6f18193..3e5ee2b 100644
--- a/linux/my_application.cc
+++ b/linux/my_application.cc
@@ -48,17 +48,17 @@ static void my_application_activate(GApplication* application) {
   }
 
   gtk_window_set_default_size(window, 1280, 720);
-  gtk_widget_show(GTK_WIDGET(window));
 
   g_autoptr(FlDartProject) project = fl_dart_project_new();
   fl_dart_project_set_dart_entrypoint_arguments(project, self->dart_entrypoint_arguments);
 
   FlView* view = fl_view_new(project);
-  gtk_widget_show(GTK_WIDGET(view));
   gtk_container_add(GTK_CONTAINER(window), GTK_WIDGET(view));
 
   fl_register_plugins(FL_PLUGIN_REGISTRY(view));
 
+  gtk_widget_show(GTK_WIDGET(window));
+  gtk_widget_show(GTK_WIDGET(view));
   gtk_widget_grab_focus(GTK_WIDGET(view));
 }
 

I somehow didn't feel like this was a pretty enough solution for proposing a change to the official Flutter app template. I'd much rather fix FlView so that it works with the original proposal...

[larsb24]

Hmm okay, understandable.
So FLView would need a fix for moving only gtk_widget_show(window) down, because the default embedder wouldn't load properly, is what I understand from that.
I personally don't really have enough experience with the embedder for that, tbh. I just thought that maybe it would be enough to PR the change that moves both gtk_widget_show(GTK_WIDGET(window)) and gtk_widget_show(GTK_WIDGET(view)) down into the template, as it technically works for both the default and the handy_window embedder.

[jpnurmi]

I have a fix proposal that feels reasonable: jpnurmi/engine@cf68162. It's probably going to be more effort to write a PR description. :)

[jpnurmi]

First step done:

• [Linux] app template should register plugins before showing the window flutter/flutter#118269