From 6e087bd7de144884288d2318cc6ac2a70abca25d Mon Sep 17 00:00:00 2001
From: Tim Holy <tim.holy@gmail.com>
Date: Wed, 9 Sep 2015 04:33:11 -0500
Subject: [PATCH] Add @guarded for creating callbacks that don't corrupt Gtk
 state

---
 src/base.jl          | 30 ++++++++++++++++++++++++++++++
 src/basic_exports.jl |  2 ++
 test/misc.jl         | 36 ++++++++++++++++++++++++++++++++++++
 test/runtests.jl     |  1 +
 4 files changed, 69 insertions(+)
 create mode 100644 test/misc.jl

diff --git a/src/base.jl b/src/base.jl
index 635253fc..492752ee 100644
--- a/src/base.jl
+++ b/src/base.jl
@@ -54,6 +54,36 @@ function setproperty!(w::GtkContainer, name::StringLike, child::GtkWidget, value
     w
 end
 
+# Shortcut for creating callbacks that don't corrupt Gtk state if
+# there's an error
+macro guarded(ex...)
+    retval = nothing
+    if length(ex) == 2
+        retval = ex[1]
+        ex = ex[2]
+    else
+        length(ex) == 1 || error("@guarded requires 1 or 2 arguments")
+        ex = ex[1]
+    end
+    isa(ex, Expr) && (
+        ex.head == :-> ||
+        (ex.head == :(=) && isa(ex.args[1],Expr) && ex.args[1].head == :call) ||
+        ex.head == :function
+    ) || error("@guarded requires an expression defining a function")
+    newbody = quote
+        begin
+            try
+                $(ex.args[2])
+            catch err
+                warn("Error in @guarded callback")
+                Base.display_error(err, catch_backtrace())
+                $retval
+            end
+        end
+    end
+    esc(Expr(ex.head, ex.args[1], newbody))
+end
+
 @deprecate getindex(w::GtkContainer, child::GtkWidget, name::StringLike, T::Type) getproperty(w,name,child,T)
 @deprecate setindex!(w::GtkContainer, value, child::GtkWidget, name::StringLike, T::Type) setproperty!(w,name,child,T,value)
 @deprecate setindex!(w::GtkContainer, value, child::GtkWidget, name::StringLike) setproperty!(w,name,child,value)
diff --git a/src/basic_exports.jl b/src/basic_exports.jl
index b9f336c7..9eaf8f83 100644
--- a/src/basic_exports.jl
+++ b/src/basic_exports.jl
@@ -22,6 +22,8 @@ export add_events, signal_emit,
     on_signal_destroy, on_signal_button_press,
     on_signal_button_release, on_signal_motion
 
+export @guarded
+
 # Tk-compatibility (reference of potentially missing functionality):
 #export Frame, Labelframe, Notebook, Panedwindow
 #export Button
diff --git a/test/misc.jl b/test/misc.jl
new file mode 100644
index 00000000..cb710aaf
--- /dev/null
+++ b/test/misc.jl
@@ -0,0 +1,36 @@
+module TestGuarded
+
+using Gtk
+
+const unhandled = convert(Cint, false)
+
+foo1 = @guarded (x,y) -> x+y
+bar1 = @guarded (x,y) -> x+y+k
+@guarded foo2(x,y) = x+y
+@guarded bar2(x,y) = x+y+k
+@guarded function foo3(x,y)
+    x+y
+end
+@guarded function bar3(x,y)
+    x+y+k
+end
+@guarded unhandled function bar4(x,y)
+    x+y+k
+end
+
+print_with_color(:green, """
+The following messages:
+   WARNING: Error in @guarded callback
+   ERROR: UndefVarError: k not defined
+are expected and a sign of normal operation.
+""")
+
+@assert foo1(3,5) == 8
+@assert bar1(3,5) == nothing
+@assert foo2(3,5) == 8
+@assert bar2(3,5) == nothing
+@assert foo3(3,5) == 8
+@assert bar3(3,5) == nothing
+@assert bar4(3,5) == unhandled
+
+end
diff --git a/test/runtests.jl b/test/runtests.jl
index 0078536e..36682466 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -1,4 +1,5 @@
 module GtkTestModule
 include("gui.jl")
 include("glib.jl")
+include("misc.jl")
 end