[gtk] (77 commits) ...Merge branch 'wip/ebassi/constraint-layout' into 'master'

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  6b308cd... Add constraint solver (*)
  c694dd6... Move the Root interface to a private header (*)
  98a21bf... Assign a GtkConstraintSolver to each GtkRoot (*)
  e07098d... window: Create a GtkConstraintSolver (*)
  e7b2c53... Propagate rooting and unrooting widgets to layout managers (*)
  cdf80f1... Add GtkConstraintLayout (*)
  636fbc0... Add GtkConstraintLayout demo (*)
  bd2349c... Do not leak LayoutChild instances (*)
  0531e66... constraint solver: Fix thawing (*)
  a246d8c... constraints solver: Avoid critials (*)
  64afa76... Do not release reference on the subject of an expression (*)
  176d9c6... Add gtk_constraint_layout_remove_constraint (*)
  a39bbb2... constraints: Make internal consistency required (*)
  21450d5... Remove size constraints from ConstraintLayoutChild (*)
  54104b6... Fix the opposite size measurement in GtkConstraintLayout (*)
  b6781e0... Notify a layout change when adding and removing constraints (*)
  04562a7... Add GtkConstraintTarget (*)
  895e8e2... widget: Implement GtkConstraintTarget (*)
  39c284c... Redefine constraints with GtkConstraintTarget (*)
  7ae04ba... Use generic pointers for constraint targets (*)
  38d353d... Add GtkConstraintGuide (*)
  7c96326... Make the constraints demo more interesting (*)
  ba2125d... Add an interactive constraints demo (*)
  92d3d55... Remove GtkConstraintVariable.set_prefix() (*)
  5ea8167... Add VFL parser for constraints (*)
  859c95b... Allow adding constraints described through VFL (*)
  46430ea... Add Constraints/VFL demo (*)
  06c825d... Add a C convenience function for VFL constraints (*)
  3204347... Add method to remove all constraints from a layout (*)
  651adbf... Return the list of constraints added via VFL description (*)
  4f4ba8c... Simplify the guide implementation (*)
  61b4feb... Detach guides on unroot (*)
  60fb909... Drop an indirection (*)
  139a59c... Flesh out GtkConstraintGuide (*)
  47237d3... demo: Use constraint guide api (*)
  2f97134... Amend a constraint solver test (*)
  3d3a672... constraint solver: Fix repeat suggestions (*)
  8b9c5e3... solver: Fix a copy/paste error (*)
  dab8a8b... constraint layout: Measure more correctly (*)
  c7ef841... constraint guide: Shorten names (*)
  b39a5fe... constraint guide: Add a name property (*)
  5a019bf... constraints demo: Give space a name (*)
  90f8dcc... constraint layout: Add debug output for guides (*)
  b1f0f44... constraint layout: Use stays for natural size (*)
  3f36340... constraint layout: Measure min/nat size separately (*)
  511e2b4... constraints: Use better data structures (*)
  f62fc4e... constraint layout: freeze/thaw on mass ops (*)
  71b52f4... constraints demo: Update comments (*)
  a9dfca0... constraint guide: Make strength tweakable (*)
  e3c4fb6... constraints: Add some internal apis (*)
  9edf6fb... constraint layout: Dont reset constraints in allocate (*)
  cb96b34... solver: Add private statistics api (*)
  405121b... constraint solver: Use GTK_NOTE (*)
  f2d7433... constraint guide: Fix initial property values (*)
  499738c... constraint guide: Avoid redundant constraints (*)
  035baa0... Mark the layout as changed (*)
  9a46305... constraint layout: Notice when guides change (*)
  514de0b... Add a constraint editor demo (*)
  d45a662... Move the VFL error domain to a public header (*)
  74c626f... Document GtkConstraintGuide (*)
  46403ba... docs: Add GtkConstraint and friends to the API reference (*)
  68fed63... Add missing documentation for GtkConstraint (*)
  c76c1a4... Remove specialised API from GtkConstraint (*)
  7990b24... Add gtkconstraintguide.h to the public headers (*)
  2aabd64... Fix warnings from the introspection scanner (*)
  c88e7c1... constraint layout: Use stronger force for min size (*)
  b224df8... constraint layout: go back to keeping constraints (*)
  670fc5b... constraint editor: Enable max size for guide (*)
  658397f... Documentation fixes (*)
  48e6cd4... constraint editor: Allow dragging children (*)
  4dd1de4... Use explicit values for constraint strength (*)
  b435dc4... Use the right GValue getter for GtkConstraintGuide:strength (*)
  6bc156c... Implement GtkBuildable for GtkConstraintLayout (*)
  8ab609e... Add custom parser for guides defined in GtkBuilder UI files (*)
  d5f8e1b... docs: Fix typo in function name (*)
  04aaf02... docs: Add more private headers to the list (*)
  b2f15a6... Merge branch 'wip/ebassi/constraint-layout' into 'master'

(*) This commit already existed in another branch; no separate mail sent