Merge pull request #36 from tkf/maxpayload

davidanthoff · web-flow · commit 44225af10578 · 2019-10-11T20:41:28.000-07:00
Add max_json_bytes to avoid sending large JSON
diff --git a/src/ElectronDisplay.jl b/src/ElectronDisplay.jl
@@ -10,6 +10,7 @@ Base.@kwdef mutable struct ElectronDisplayConfig
     showable = electron_showable
     single_window::Bool = false
     focus::Bool = true
+    max_json_bytes::Int = 2^20
 end
 
 """
@@ -22,11 +23,13 @@ setconfig(
     showable = config.showable,
     single_window::Bool = config.single_window,
     focus::Bool = config.focus,
+    max_json_bytes::Int = config.max_json_bytes,
 ) =
     ElectronDisplayConfig(
         showable = showable,
         single_window = single_window,
         focus = focus,
+        max_json_bytes = max_json_bytes,
     )
 
 struct ElectronDisplayType <: Base.AbstractDisplay
@@ -57,6 +60,11 @@ Configuration for ElectronDisplay.
 
 * `focus::Bool = true`: Focus the Electron window on `display` if `true`
   (default).
+
+* `max_json_bytes::Int = $(ElectronDisplayConfig().max_json_bytes)`:
+  Maximum size in bytes for which JSON representation is used.  Otherwise,
+  convert visualization locally in a binary form before sending it to the
+  Electron display.  Currently only Vega and Vega-Lite support this.
 """
 const CONFIG = ElectronDisplayConfig()
 
diff --git a/src/vega.jl b/src/vega.jl
@@ -4,8 +4,22 @@ Base.displayable(d::ElectronDisplayType, ::MIME{Symbol("application/vnd.vega.v3+
 Base.displayable(d::ElectronDisplayType, ::MIME{Symbol("application/vnd.vega.v4+json")}) = true
 Base.displayable(d::ElectronDisplayType, ::MIME{Symbol("application/vnd.vega.v5+json")}) = true
 
+function _maybe_fallback_to(mime, d, x, payload)
+    if sizeof(payload) > d.config.max_json_bytes
+        @warn string(
+            "The size of JSON representation (", sizeof(payload), ")",
+            " exceeds `max_json_bytes = ", d.config.max_json_bytes, "`.",
+            " Falling back to $mime."
+        )
+        return display(d, mime, x)
+    end
+    return nothing
+end
+
 function _display_vegalite(d, major_version_vegalite, major_version_vega, x)
     payload = stringmime(MIME("application/vnd.vegalite.v$major_version_vegalite+json"), x)
+    ans = _maybe_fallback_to(MIME"image/png"(), d, x, payload)
+    ans === nothing || return ans
 
     html_page = """
     <html>
@@ -49,6 +63,8 @@ end
 
 function _display_vega(d, major_version, x)
     payload = stringmime(MIME("application/vnd.vega.v$major_version+json"), x)
+    ans = _maybe_fallback_to(MIME"image/png"(), d, x, payload)
+    ans === nothing || return ans
 
     html_page = """
     <html>
diff --git a/test/construct_vega_specs.jl b/test/construct_vega_specs.jl
@@ -318,3 +318,20 @@ vg5 = DummyDisplayable{MIME"application/vnd.vega.v5+json"}("""
   ]
 }
 """)
+
+# based on https://github.com/mathiasbynens/small
+dummy_png_bytes = UInt8[
+    0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a, 0x00, 0x00, 0x00, 0x0d,
+    0x49, 0x48, 0x44, 0x52, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x01,
+    0x08, 0x06, 0x00, 0x00, 0x00, 0x1f, 0x15, 0xc4, 0x89, 0x00, 0x00, 0x00,
+    0x0a, 0x49, 0x44, 0x41, 0x54, 0x78, 0x9c, 0x63, 0x00, 0x01, 0x00, 0x00,
+    0x05, 0x00, 0x01,
+]
+
+struct DummyVegaLitePNGHybrid end
+Base.show(io::IO, ::MIME"application/vnd.vegalite.v3+json", ::DummyVegaLitePNGHybrid) =
+    print(io, vl3)
+Base.show(io::IO, ::MIME"image/png", ::DummyVegaLitePNGHybrid) =
+    write(io, dummy_png_bytes)
+
+vl3png = DummyVegaLitePNGHybrid()
diff --git a/test/runtests.jl b/test/runtests.jl
@@ -40,6 +40,11 @@ eldt = ElectronDisplay.ElectronDisplayType()
 @test electrondisplay(vg4) isa Electron.Window
 @test electrondisplay(vg5) isa Electron.Window
 
+@test_logs(
+    (:warn, r"The size of JSON representation.*exceeds.*max_json_bytes"),
+    electrondisplay(vl3png; max_json_bytes=-1)::Electron.Window
+)
+
 mdo = DummyDisplayable{MIME"text/markdown"}("""foo""")
 @test electrondisplay(mdo) isa Electron.Window
 
