Title location and alignment

src/backends/gr.jl

@@ -41,8 +41,18 @@ gr_markertype(k) = (
     hline = -31,
 )[k]
 
-gr_halign(k) = (left = 1, hcenter = 2, right = 3)[k]
-gr_valign(k) = (top = 1, vcenter = 3, bottom = 5)[k]
+gr_halign(k) = (
+    left = GR.TEXT_HALIGN_LEFT,
+    hcenter = GR.TEXT_HALIGN_CENTER,
+    center = GR.TEXT_HALIGN_CENTER,
+    right = GR.TEXT_HALIGN_RIGHT,
+)[k]
+gr_valign(k) = (
+    top = GR.TEXT_VALIGN_TOP,
+    vcenter = GR.TEXT_VALIGN_HALF,
+    center = GR.TEXT_VALIGN_HALF,
+    bottom = GR.TEXT_VALIGN_BOTTOM,
+)[k]
 
 const gr_font_family = Dict(
     # compat
@@ -1814,17 +1824,22 @@ function gr_add_title(sp, viewport_plotarea, viewport_subplot)
         gr_set_font(titlefont(sp), sp)
         loc = sp[:titlelocation]
         if loc === :left
-            xpos = viewport_plotarea[1]
-            halign = GR.TEXT_HALIGN_LEFT
+            xpos, ypos = viewport_plotarea[1], viewport_subplot[4]
+            halign, valign = GR.TEXT_HALIGN_LEFT, GR.TEXT_VALIGN_TOP
+        elseif loc === :center
+            xpos, ypos = +(viewport_plotarea[1:2]...) / 2, viewport_subplot[4]
+            halign, valign = GR.TEXT_HALIGN_CENTER, GR.TEXT_VALIGN_TOP
         elseif loc === :right
-            xpos = viewport_plotarea[2]
-            halign = GR.TEXT_HALIGN_RIGHT
+            xpos, ypos = viewport_plotarea[2], viewport_subplot[4]
+            halign, valign = GR.TEXT_HALIGN_RIGHT, GR.TEXT_VALIGN_TOP
         else
-            xpos = gr_view_xcenter(viewport_plotarea)
-            halign = GR.TEXT_HALIGN_CENTER
+            xpos = gr_view_xposition(viewport_plotarea, loc[1])
+            ypos = gr_view_yposition(viewport_plotarea, loc[2])
+            halign = gr_halign(sp[:titlefonthalign])
+            valign = gr_valign(sp[:titlefontvalign])
         end
-        GR.settextalign(halign, GR.TEXT_VALIGN_TOP)
-        gr_text(xpos, viewport_subplot[4], sp[:title])
+        GR.settextalign(halign, valign)
+        gr_text(xpos, ypos, sp[:title])
         GR.restorestate()
     end
 end

src/backends/pgfplotsx.jl

@@ -85,6 +85,8 @@ curly(obj) = "{$(string(obj))}"
 latex_formatter(formatter::Symbol) = formatter in (:plain, :latex) ? formatter : :latex
 latex_formatter(formatter::Function) = formatter
 
+pgfx_halign(k) = (left = "left", hcenter = "center", center = "center", right = "right")[k]
+
 function (pgfx_plot::PGFPlotsXPlot)(plt::Plot{PGFPlotsXBackend})
     if !pgfx_plot.is_created || pgfx_plot.was_shown
         pgfx_sanitize_plot!(plt)
@@ -150,6 +152,7 @@ function (pgfx_plot::PGFPlotsXPlot)(plt::Plot{PGFPlotsXBackend})
                     "color" => title_cstr,
                     "draw opacity" => alpha(title_cstr),
                     "rotate" => sp[:titlefontrotation],
+                    "align" => pgfx_halign(sp[:titlefonthalign]),
                 ),
                 "legend style" => pgfx_get_legend_style(sp),
                 "axis background/.style" =>

src/backends/plotly.jl

@@ -219,20 +219,28 @@ function plotly_layout(plt::Plot)
     for sp in plt.subplots
         spidx = multiple_subplots ? sp[:subplot_index] : ""
         x_idx, y_idx = multiple_subplots ? plotly_link_indicies(plt, sp) : ("", "")
-        # add an annotation for the title... positioned horizontally relative to plotarea,
-        # but vertically just below the top of the subplot bounding box
+
+        # add an annotation for the title
         if sp[:title] != ""
             bb = plotarea(sp)
             tpos = sp[:titlelocation]
-            xmm = if tpos === :left
-                left(bb)
+            if tpos === :left
+                xmm, ymm = left(bb), top(bbox(sp))
+                halign, valign = :left, :top
+            elseif tpos === :center
+                xmm, ymm = 0.5 * (left(bb) + right(bb)), top(bbox(sp))
+                halign, valign = :hcenter, :top
             elseif tpos === :right
-                right(bb)
+                xmm, ymm = right(bb), top(bbox(sp))
+                halign, valign = :right, :top
             else
-                0.5 * (left(bb) + right(bb))
+                xmm = left(bb) + tpos[1] * width(bb)
+                # inverting to make consistent with GR
+                ymm = bottom(bb) - tpos[2] * height(bb)
+                halign, valign = sp[:titlefonthalign], sp[:titlefontvalign]
             end
-            titlex, titley = xy_mm_to_pcts(xmm, top(bbox(sp)), w * px, h * px)
-            title_font = font(titlefont(sp), :top)
+            titlex, titley = xy_mm_to_pcts(xmm, ymm, w * px, h * px)
+            title_font = font(titlefont(sp), halign = halign, valign = valign)
             push!(
                 plotattributes_out[:annotations],
                 plotly_annotation_dict(titlex, titley, text(sp[:title], title_font)),