Class: Emfsvg::TransformStack

Inherits:
Object
  • Object
show all
Defined in:
lib/emfsvg/transform_stack.rb

Overview

SaveDC/RestoreDC stack of DeviceContext snapshots.

IMPORTANT: libemf2svg's restoreDeviceContext WALKS the stack to find the target level but does NOT remove entries — the same save can be restored multiple times. This mirrors Windows GDI behavior where RestoreDC's saved_dc argument identifies a level (not a one-shot pop). We replicate that exactly: restore() reads the target snapshot but leaves the stack intact.

Instance Method Summary collapse

Constructor Details

#initialize ⇒ TransformStack

Returns a new instance of TransformStack.



13
14
15
 
# File 'lib/emfsvg/transform_stack.rb', line 13

def initialize
  @stack = []
end

Instance Method Details

#push(dc) ⇒ Object 



17
18
19
 
# File 'lib/emfsvg/transform_stack.rb', line 17

def push(dc)
  @stack.push(dc.dup)
end

#restore(saved_dc) ⇒ Object

Returns the snapshot at the target level. The stack is NOT modified. saved_dc semantics match libemf2svg: negative N = "N levels back from the top" (so -1 is the top, -2 is one below, etc.); positive N is treated as the equivalent 1-based absolute level.



25
26
27
28
29
30
31
32
33
34
 
# File 'lib/emfsvg/transform_stack.rb', line 25

def restore(saved_dc)
  target_index = if saved_dc.negative?
                   @stack.size + saved_dc
                 else
                   saved_dc - 1
                 end
  return nil if target_index.negative? || target_index >= @stack.size

  @stack[target_index]
end

#size ⇒ Object 



36
37
38
 
# File 'lib/emfsvg/transform_stack.rb', line 36

def size
  @stack.size
end