prelim work on adding optional runtime backend loading

GiovineItalia · Jul 29, 2018 · 4e20db6 · 4e20db6
1 parent b96083d
commit 4e20db6
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Showing 2 changed files with 27 additions and 45 deletions.
diff --git a/REQUIRE b/REQUIRE
@@ -5,3 +5,4 @@ DataStructures
 IterTools
 JSON
 Measures
+Requires
diff --git a/src/Compose.jl b/src/Compose.jl
@@ -7,6 +7,7 @@ using IterTools
 using DataStructures
 using Compat
 using Measures
+using Requires
 import JSON
 
 import Base: length, start, next, done, isempty, getindex, setindex!,
@@ -15,7 +16,6 @@ import Base: length, start, next, done, isempty, getindex, setindex!,
 
 using Compat.Dates
 using Compat.Printf
-using Compat.Pkg
 
 import Measures: resolve, w, h
 
@@ -31,25 +31,6 @@ export compose, compose!, Context, UnitBox, AbsoluteBoundingBox, Rotation, Mirro
        CAIROSURFACE, introspect, set_default_graphic_size, set_default_jsmode,
        boundingbox, Patchable
 
-function isinstalled(pkg, ge=v"0.0.0-")
-    try
-        # Pkg.installed might throw an error,
-        # we need to account for it to be able to precompile
-        ver = Pkg.installed(pkg)
-        ver == nothing && try
-            # Assume the version is new enough if the package is in LOAD_PATH
-            ex = Expr(:import, Symbol(pkg))
-            @eval $ex
-            return true
-        catch
-            return false
-        end
-        return ver >= ge
-    catch
-        return false
-    end
-end
-
 abstract type Backend end
 
 """
@@ -157,40 +138,40 @@ macro missing_cairo_error(backend)
     string(msg1, msg2)
 end
 
-if isinstalled("Cairo")
-    include("cairo_backends.jl")
-    include("immerse_backend.jl")
-else
-    global PNG
-    global PS
-    global PDF
-
-    PNG(args...) = error(@missing_cairo_error "PNG")
-    PS(args...) = error(@missing_cairo_error "PS")
-    PDF(args...) = error(@missing_cairo_error "PDF")
-end
+global PDF
+PNG(args...) = error(@missing_cairo_error "PNG")
+PS(args...) = error(@missing_cairo_error "PS")
+PDF(args...) = error(@missing_cairo_error "PDF")
+
 include("svg.jl")
 include("pgf_backend.jl")
 
 # If available, pango and fontconfig are used to compute text extents and match
 # fonts. Otherwise a simplistic pure-julia fallback is used.
 
-if isinstalled("Fontconfig")
+include("fontfallback.jl")
+
+function link_fontconfig()
     pango_cairo_ctx = C_NULL
     include("pango.jl")
 
-    function __init__()
-        global pango_cairo_ctx
-        global pangolayout
-        ccall((:g_type_init, Cairo._jl_libgobject), Cvoid, ())
-        pango_cairo_fm  = ccall((:pango_cairo_font_map_new, libpangocairo),
-                                 Ptr{Cvoid}, ())
-        pango_cairo_ctx = ccall((:pango_font_map_create_context, libpango),
-                                 Ptr{Cvoid}, (Ptr{Cvoid},), pango_cairo_fm)
-        pangolayout = PangoLayout()
-    end
-else
-    include("fontfallback.jl")
+    ccall((:g_type_init, Cairo._jl_libgobject), Cvoid, ())
+    pango_cairo_fm  = ccall((:pango_cairo_font_map_new, libpangocairo),
+                             Ptr{Cvoid}, ())
+    pango_cairo_ctx = ccall((:pango_font_map_create_context, libpango),
+                             Ptr{Cvoid}, (Ptr{Cvoid},), pango_cairo_fm)
+    pangolayout = PangoLayout()
+end
+
+function link_cairo()
+    @info "Loading Cairo backend into Compose.jl"
+    include("cairo_backends.jl")
+    include("immerse_backend.jl")
+end
+
+function __init__()
+    @require Cairo="159f3aea-2a34-519c-b102-8c37f9878175" link_cairo()
+    @require Fontconfig="186bb1d3-e1f7-5a2c-a377-96d770f13627" link_fontconfig()
 end
 
 show(io::IO, m::MIME"text/html", ctx::Context) =